Deposition methods for high quality reflectance coatings

ABSTRACT

Low-emissivity coatings that are highly reflective to infrared-radiation. The coating includes three infrared-reflection film regions, which may each include silver.

RELATED APPLICATIONS

The present application is a continuation of U.S. utility applicationSer. No. 15/175,401, filed Jun. 7, 2016, which is a continuation of U.S.utility application Ser. No. 14/052,975, filed Oct. 14, 2013, issued asU.S. Pat. No. 9,376,853, which is a continuation of U.S. utilityapplication Ser. No. 13/646,873, filed Oct. 8, 2012, issued as U.S. Pat.No. 8,586,215, which is a continuation of U.S. utility application Ser.No. 12/851,269, filed Aug. 5, 2010, issued as U.S. Pat. No. 8,283,059,which is a continuation of U.S. utility application Ser. No. 11/546,152,filed Oct. 11, 2006, now abandoned, which in turn is acontinuation-in-part of U.S. utility application Ser. No. 11/398,345,filed Apr. 5, 2006, issued as U.S. Pat. No. 7,342,716, which in turn isa continuation-in-part of U.S. utility application Ser. No. 11/360,266,filed Feb. 23, 2006, issued as U.S. Pat. No. 7,339,728, which in turnclaims priority to U.S. provisional application No. 60/725,891, filedOct. 11, 2005, the entire contents of each which are incorporated hereinby reference.

FIELD OF THE INVENTION

The present invention relates to thin film coatings for glass and othersubstrates. In particular, this invention relates to low-emissivitycoatings that are reflective of infrared radiation. Also provided aremethods and equipment for depositing thin film coatings.

BACKGROUND OF THE INVENTION

Low-emissivity coatings are well known in the art. Typically, theyinclude one or two layers of infrared-reflection film and two or morelayers of transparent dielectric film. The infrared-reflection film,which generally is a conductive metal like silver, gold, or copper,reduces the transmission of heat through the coating. The dielectricfilms are used to anti-reflect the infrared-reflection films in selectedspectral regions (visible region of sun light) and to control otherproperties and characteristics of the coating, such as color anddurability. Commonly used dielectric materials include oxides of zinc,tin, indium, bismuth, and titanium, among others.

Most commercially available low-emissivity coatings have one or twosilver layers each sandwiched between two coats of transparentdielectric film. Increasing the number of silver films in alow-emissivity coating can increase its infrared reflection. Incommercial coating processes the Ag films are supported by growthsupport layers (below) and protective layers above. Especially theprotective layers above can add some additional (to the silver films)absorption to the layer-stack. For multiple silver films in a layerstack this can add up to total absorption levels not acceptable for someapplications. This will also reduce the visible transmission of thecoating, and/or negatively impact the color of the coating, and/ordecrease the durability of the coating. In some processes, growthsupport layers are provided beneath silver films and protective layersare provided above silver films. An increase in the number of growthsupport layers and protective layers in a low-emissivity coating canincrease the overall absorption of the coating. This can be undesirablein some cases. Perhaps for these reasons, low-emissivity coatings withthree silver layers have not found much place in the market.

It would be desirable to provide a low-emissivity coating that includesthree infrared-reflection film regions and has desirable coatingproperties and characteristics. It would also be desirable to providedeposition methods and equipment that can produce high quality coatingsof this nature.

SUMMARY OF THE INVENTION

In certain embodiments, the invention provides a method for depositingfilm onto a glass sheet. In the present embodiments, the methodcomprises providing a coater having a path of substrate travel extendingthrough the coater.

The following description uses as an example a coater with horizontalsubstrate transport (referring to coating down and up to cover bothsurfaces).

It is well known that the same purposes can be achieved with a coaterusing (nearly) vertical glass transport. In such cases, the coatingdirections “up” and “down” are to be replaced by: left and right.

The expression “sputtering” or “magnetron sputtering” stand for thecurrently most common coating method, but it is obvious that any (largearea) vacuum coating method can be used instead.

In-line with these coating stations can be treatment stations which areused to heat, cool, clean, activate or accomplish some plasma peeningaction.

It is also implied that if during the travel of substrates through thecoating line different gas (mixes) and pressures are to be applieddynamic gas separation sections can be present.

Preferably, the coater includes downward coating equipment mounted abovethe path of substrate travel. The glass sheet is conveyed along the pathof substrate travel in a generally horizontal orientation wherein a topmajor surface of the glass sheet is oriented upwardly and a bottom majorsurface of the glass sheet is oriented downwardly. The downward coatingequipment is operated to deposit upon the top major surface of the glasssheet a coating that includes a sequence of at least seven film regionscomprising, moving outwardly from the top major surface of the glasssheet, a first transparent dielectric film region, a firstinfrared-reflective film region comprising silver, a second transparentdielectric film region, a second infrared-reflective film regioncomprising silver, a third transparent dielectric film region, a thirdinfrared-reflective film region comprising silver, and a fourthtransparent dielectric film region. In the present embodiments, themethod comprises depositing the noted film regions in a single pass ofthe glass sheet through the coater, and during this single pass theglass sheet is conveyed at a conveyance rate exceeding 275 inches perminute. A transparent dielectric film region can be made up frommultiple sub-layers of different materials. These materials could,besides being chosen for their optical properties, be chosen to optimizeelectrical, mechanical, and/or chemical properties of the wholelayer-stack before and/or after any optional heat treatment. In some ofthe present embodiments, the coater has an extended series of chambersincluding at least 60 sputtering chambers, the useful coating width hasa major dimension of at least 2 meters, and the method comprisesentirely coating both the top and bottom major surfaces of the glasssheet in the single pass of the glass sheet through the coater.

Certain embodiments of the invention provide a coater having an extendedseries of sputtering chambers and a substrate support defining a path ofsubstrate travel extending through all the sputtering chambers of thecoater. The substrate support (which in some embodiments comprisetransport rollers, and in other embodiments comprises a conveyor orcarriers) is adapted for conveying along the path of substrate travel asheet-like substrate (such as a glass or plastic sheet) having multiplemajor dimensions optionally of greater than 2.0 meters. In the presentembodiments, the coater has an upward sputtering section and a downwardsputtering section.

There can also be sections sputtering up and down at the same time andlocation. The upward sputtering section is characterized by a series oflower targets mounted at lower elevation than the path of substratetravel, and the downward sputtering section is characterized by a seriesof upper targets mounted at higher elevation than the path of substratetravel. In the present embodiments, the downward sputtering section hasat least 39 downward sputtering chambers each including at least one ofthe upper targets, and the upward sputtering section has a plurality ofupward sputtering chambers each including at least one of the lowertargets. In these embodiments, the downward sputtering chambers form atleast seven downward deposition systems comprising, in sequence alongthe path of substrate travel, a first downward deposition system adaptedfor depositing a first transparent dielectric film region, a seconddownward deposition system adapted for depositing a firstinfrared-reflective film region comprising silver, a third downwarddeposition system adapted for depositing a second transparent dielectricfilm region, a fourth downward deposition system adapted for depositinga second infrared-reflective film region comprising silver, a fifthdownward deposition system adapted for depositing a third transparentdielectric film region, a sixth downward deposition system adapted fordepositing a third infrared-reflective film region comprising silver,and a seventh downward deposition system adapted for depositing a fourthtransparent dielectric film region.

In certain embodiments, the invention provides a method for depositingfilm onto a glass sheet. In the present embodiments, the method involvesproviding a coater having an extended series of sputtering chambers anda path of substrate travel extending through all the sputtering chambersof the coater. In this group of embodiments, the coater's extendedseries of chambers includes at least 60 sputtering chambers, at leastsome of which are adapted for downward sputtering and include uppersputtering targets mounted above the path of substrate travel. The glasssheet is conveyed along the path of substrate travel, preferably in agenerally horizontal orientation wherein a top major surface of theglass sheet is oriented upwardly and a bottom major surface of the glasssheet is oriented downwardly. In the present embodiments, the glasssheet is conveyed along at least a portion of the path of substratetravel at a conveyance rate of 300 inches per minute or faster, and atleast a plurality of the upper targets are sputtered to deposit upon thetop major surface of the glass sheet a coating comprising, movingoutwardly from the top major surface of the glass sheet, a firsttransparent dielectric film region, a first infrared-reflective filmregion comprising silver, a second transparent dielectric film region, asecond infrared-reflective film region comprising silver, a thirdtransparent dielectric film region, a third infrared-reflective filmregion comprising silver, and a fourth transparent dielectric filmregion.

Certain embodiments of the invention provide a method for depositingfilm onto a sheet-like substrate. In the present embodiments, the methodinvolves providing a coater having an extended series of sputteringchambers and a path of substrate travel extending through all thesputtering chambers of the coater. In these embodiments, the coater'sextended series of sputtering chambers preferably includes at least 60sputtering chambers at least some of which are adapted for downwardsputtering and include upper sputtering targets mounted above the pathof substrate travel. The substrate is conveyed along the path ofsubstrate travel, preferably in a generally horizontal orientationwherein a top major surface of the substrate is oriented upwardly and abottom major surface of the substrate is oriented downwardly. In thepresent embodiments, the substrate is conveyed along at least a portionof the path of travel at a conveyance rate exceeding 275 inches perminute. In the present embodiments, two series of the upper targets aresputtered in nitriding gas (optionally a mix of oxygen and nitrogen) toreactively sputter deposit over the top major surface of the substratetwo transparent dielectric nitride film regions (the films may consistessentially of nitride, they may comprise oxynitride film, etc.), and aninfrared-reflective film region is deposited between these twotransparent dielectric nitride film regions. Here, the two notedtransparent dielectric nitride film regions (and the infrared-reflectivefilm region(s) between them) are part of a coating comprising, movingoutwardly from the top major surface of the substrate, a firsttransparent dielectric film region, a first infrared-reflective filmregion comprising silver, a second transparent dielectric film region, asecond infrared-reflective film region comprising silver, a thirdtransparent dielectric film region, a third infrared-reflective filmregion comprising silver, and a fourth transparent dielectric filmregion.

In certain embodiments, the invention provides a method for depositingfilm onto a glass sheet. The method involves providing a coater havingan extended series of sputtering chambers and a path of substrate travelextending through all the sputtering chambers of the coater. In thepresent embodiments, the coater's extended series of sputtering chambersincludes at least 63 sputtering chambers at least some of which areadapted for downward sputtering and include upper sputtering targetsmounted above the path of substrate travel. The glass sheet is conveyedalong the path of substrate travel, preferably in a generally horizontalorientation wherein a top major surface of the glass sheet is orientedupwardly and a bottom major surface of the glass sheet is orienteddownwardly. In the present embodiments, the glass sheet is conveyedalong at least a portion of the path of substrate travel at a conveyancerate of 300 inches per minute or faster. In the present embodiments, twoseries of the upper targets are sputtered in nitriding gas to reactivelysputter deposit (over the top major surface of the substrate) twotransparent dielectric nitride film regions. At least oneinfrared-reflective film region is deposited between these twotransparent dielectric nitride film regions, and the two notedtransparent dielectric nitride film regions (and the infrared-reflectivefilm region(s) between them), are part of a coating comprising, movingoutwardly from the top major surface of the substrate, a firsttransparent dielectric film region, a first infrared-reflective filmregion comprising silver, a second transparent dielectric film region, asecond infrared-reflective film region comprising silver, a thirdtransparent dielectric film region, a third infrared-reflective filmregion comprising silver, and a fourth transparent dielectric filmregion. In the present embodiments, the method comprises sputterdepositing dielectric film directly over at least one of the three notedinfrared-reflective film regions comprising silver.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the spectral properties of a commerciallyavailable double silver low-emissivity coating.

FIG. 2 is a graph showing the spectral properties of a high infraredreflection coating in accordance with certain embodiments of the presentinvention.

FIG. 3 is a graph comparing the spectral properties of a high infraredreflection coating in accordance with certain embodiments of theinvention against a commercially available double silver low-emissivitycoating.

FIG. 4 is a schematic cross-sectional side view of a substrate bearing ahigh infrared reflection coating in accordance with certain embodimentsof the invention;

FIG. 5 is a schematic partially broken-away cross-sectional side view ofa multiple-pane insulating glazing unit bearing a high infraredreflection coating in accordance with certain embodiments of theinvention;

FIG. 6 is a schematic side view of a coating chamber in accordance withcertain embodiments of the present invention;

FIG. 7 is a schematic side view of a coating chamber in accordance withcertain embodiments of the invention;

FIG. 8 is a schematic side view of a coating chamber in accordance withcertain embodiments of the invention;

FIG. 9 is a schematic side view of a coater in accordance with certainembodiments of the invention;

FIG. 10 is a schematic side view of a coater in accordance with certainembodiments of the invention;

FIG. 11 is a schematic side view of a coater in accordance with certainembodiments of the invention;

FIG. 12 is a schematic side view of a coater in accordance with certainembodiments of the invention; and

FIG. 13 is a schematic side view of a coater in accordance with certainembodiments of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following detailed description is to be read with reference to thedrawings, in which like elements in different drawings have likereference numerals. The drawings, which are not necessarily to scale,depict selected embodiments and are not intended to limit the scope ofthe invention. Skilled artisans will recognize that the examplesprovided herein have many useful alternatives that fall within the scopeof the invention.

Single and double silver low-emissivity coatings have been known in theart for years. Single silver low-emissivity coatings provideadvantageous infrared reflection, commonly in the neighborhood of 96%.Double silver low-emissivity coatings offer further improvements interms of improved spectral selectivity and higher solar infraredreflection. There are, however, practical ceilings on the infraredreflection levels that can be achieved using a double silverlow-emissivity coating. For example, while increasing the amount ofsilver in a double silver coating may boost the infrared reflectionabove 97%, the road toward even higher infrared reflection, e.g., above98.5%, is difficult to achieve in a double silver coating having a goodbalance of other properties (high visible transmission, good color,durability, etc.).

FIG. 1 is a graph showing the spectral properties of a highlyadvantageous commercially available double silver low-emissivitycoating. This graph shows transmission (the curve that is upwardlyconvex in the visible wavelength range) and glass-side reflection (thecurve that is downwardly concave in the visible wavelength range) for aglass sheet bearing the double silver low-emissivity coating. While thisparticular double silver coating offers excellent spectral properties,it has been reported that conventional double silver coatings allowanywhere from 5% to 50% transmission in the infrared wavelength range(U.S. Pat. No. 6,262,830, column 6, lines 43-51).

FIG. 2 is a graph showing the spectral properties (in the range of solarradiation) of a high infrared reflection coating in accordance withcertain embodiments of the present invention. Here again, the graphshows transmission (the curve that is upwardly convex in the visiblewavelength range) and glass-side reflection (the curve that isdownwardly concave in the visible wavelength range) for a glass sheetbearing the high infrared reflection coating.

The solar infrared reflection of the present coating 7 is much higherthan that of the double silver coating. This is perhaps best appreciatedby referring to FIG. 3, which is a graph showing both the spectralproperties of the high infrared reflection coating 7 and those of thedouble silver coating. Here, a side-by-side comparison can be made ofthe solar infrared reflection levels achieved by these two coatings. Itcan be seen that the present coating 7 achieves a much higher infraredreflection than the double silver coating. It can also be seen that thelevels of visible transmission for these two coatings are comparable.Moreover, the cutoff between visible wavelengths and infraredwavelengths is much sharper for the present coating 7 (the curvesdelineated with solid lines) than for the double silver coating (thecurves delineated with circles). Thus, the high infrared reflectioncoating 7 provides a quantum leap forward in terms of energy efficiencycompared to double silver low-emissivity coatings, and even more socompared to single silver low-emissivity coatings.

The present high infrared reflection coating (or “multiple cavitylow-emissivity coating”) 7 has a number of beneficial properties. Theensuing discussion reports several of these properties. In some cases,properties are reported herein for a single (i.e., monolithic) pane 12bearing the present coating 7 on one surface 18. In other cases, theseproperties are reported for an IG unit 3 having the present coating 7 onits #2 surface 18. In such cases, the reported properties are for an IGunit wherein both panes are clear 2.2 mm soda lime float glass with a ½inch between-pane space filled with an insulative gas mix of 90% argonand 10% air. Of course, these specifics are by no means limiting to theinvention. Absent an express statement to the contrary, the presentdiscussion reports determinations made using the well-known WINDOW 5.2 acomputer program (e.g., calculating center of glass data) under standardASHRAE conditions.

As noted above, the high infrared reflection coating 7 providesexceptional thermal insulating properties. The coating 7 comprises threeinfrared-reflection film regions 100, 200, and 300. These film regionsare typically silver or another electrically conductive material, andthey impart exceptionally low sheet resistance in the coating. Forexample, the sheet resistance of the present coating 7 is less than 3.0Ω/square. Preferably, the sheet resistance of this coating 7 is lessthan 2.5 SI/square (e.g., less than 2.0 Ω/square, less than 1.75Ω/square, less than 1.5 Ω/square, or even less than 1.35 Ω/square).While the desired level of sheet resistance can be selected and variedto accommodate different applications, a number of preferred coatingembodiments (e.g., the exemplary film stacks tabulated below) provide asheet resistance of less than 1.4 Ω/square, such as about 1.25-1.3Ω/square. The sheet resistance of the coating can be measured instandard fashion using a 4-point probe. Other methods known in the artas being useful for calculating sheet resistance can also be used.

The coating 7 also has exceptionally low emissivity. For example, theemissivity of the coating 7 is less than 0.06. Preferably, theemissivity of this coating 7 is less than 0.04 (e.g., less than 0.03, oreven less than 0.025). While the desired level of emissivity can beselected and varied to accommodate different applications, a number ofpreferred coating embodiments (e.g., the exemplary film stacks tabulatedbelow) provide an emissivity of less than 0.023, less than 0.022, oreven less than 0.021. In one embodiment, the emissivity is about 0.020.In contrast, an uncoated pane of clear glass would typically have anemissivity of about 0.84.

The term “emissivity” is well known in the present art. This term isused herein in accordance with its well-known meaning to refer to theratio of radiation emitted by a surface to the radiation emitted by ablackbody at the same temperature. Emissivity is a characteristic ofboth absorption and reflectance. It is usually represented by theformula: E=1−Reflectance. The present emissivity values can bedetermined as specified in “Standard Test Method For Emittance OfSpecular Surfaces Using Spectrometric Measurements” NFRC 301-93, theentire teachings of which are incorporated herein by reference.Emissivity can be calculated by multiplying the measured sheetresistance by 0.016866. Using this method, a coating 7 that providessheet resistance of about 1.25 can be found to have an emissivity ofabout 0.021.

In addition to low sheet resistance and low emissivity, the presentcoating 7 provides exceptional solar heat gain properties. As is wellknown, the solar heat gain coefficient (SHGC) of a window is thefraction of incident solar radiation that is admitted through a window.There are a number of applications where low solar heat gain windows areof particular benefit. In warm climates, for example, it is especiallydesirable to have low solar heat gain windows. For example, solar heatgain coefficients of about 0.4 and below are generally recommended forbuildings in the southern United States. Further, windows that areexposed to a lot of undesirable sun benefit from having a low solar heatgain coefficient. Windows on the east or west side of a building, forinstance, tend to get a lot of sun in the morning and afternoon. Forapplications like these, the solar heat gain coefficient plays a vitalrole in maintaining a comfortable environment within the building. Thus,it is particularly beneficial to provide windows of this nature withcoatings that establish a low solar heat gain coefficient (i.e., lowsolar heat gain coatings). Low solar heat gain coatings would, in fact,be highly desirable for many window applications. However, thesecoatings have not traditionally offered high enough visible transmissionto be more broadly adopted.

A tradeoff is sometimes made in low solar heat gain coatings whereby thefilms selected to achieve a low SHGC have the effect of decreasing thevisible transmittance to a lower level than is ideal and/or increasingthe visible reflectance to a higher level than is ideal. As aconsequence, windows bearing these coatings may have unacceptably lowvisible transmission and/or a somewhat mirror-like appearance.

The present coating 7 provides an exceptionally low solar heat gaincoefficient. For example, the solar heat gain coefficient of the presentIG unit 3 is less than 0.4. Preferably, the present IG unit 3 has asolar heat gain coefficient of less than 0.35 (e.g., less than 0.33, orless than 0.31), less than 0.29, or even less than 0.28 (such as 0.27 orless). While the desired SHGC level can be selected and varied toaccommodate different applications, some preferred embodiments (e.g.,where the coating 7 is one of the exemplary film stacks tabulated below)provide an IG unit 3 having a solar heat gain coefficient of between0.25 and 0.29 (e.g., between 0.25 and 0.28, such as 0.27). The presentcoating 7 can provide a SHGC within any one or more of these rangeswhile at the same time providing exceptional color (e.g., any colorrange noted below) and/or high visible transmission (e.g., any visibletransmission range noted below). In some cases, the coating 7 providesthis balance of properties while having a surprisingly highmetal/dielectric ratio, as described below.

The term “solar heat gain coefficient” is used herein in accordance withits well-known meaning. Reference is made to NFRC 200-93 (1993), theentire teachings of which are incorporated herein by reference. The SHGCcan be calculated using the methodology embedded in the well-knownWINDOW 5.2 a computer program.

In combination with the beneficial thermal insulating propertiesdiscussed above, the present coating 7 has exceptional opticalproperties. As noted above, a tradeoff is sometimes made in low solarheat gain coatings whereby the films selected to achieve good thermalinsulating properties have the effect of restricting the visibletransmission to a level that is lower than ideal.

To the contrary, the present coating 7 provides an exceptionalcombination of total visible transmission and thermal insulatingproperties. For example, the present IG unit 3 (and the present pane 12,whether monolithic or as part of the IG unit 3) has a visibletransmittance T_(v) of greater than 0.45 (i.e., greater than 45%).Preferably, the present IG unit 3 (and the present pane 12, whethermonolithic or insulated) achieves a visible transmittance T_(v) ofgreater than 0.55 (e.g., greater than 0.6), greater than 0.63, greaterthan 0.65, or even greater than 0.72.

While the desired level of visible transmittance can be selected andvaried to accommodate different applications, certain preferredembodiments (e.g., where the coating 7 is one of the exemplary filmstacks tabulated below) provide an IG unit 3 (or a pane 12, which can bemonolithic or part of the IG unit 3) having a visible transmittance ofgreater than 0.65, such as about 0.66.

In one particular group of embodiments, the film region thicknesses andcompositions are selected to achieve a visible transmittance of greaterthan 0.7, greater than 0.71, or even greater than 0.72. In some cases,the film region thicknesses and compositions are selected to achieve avisible transmittance of about 0.73. Here, the infrared-reflection filmregions can optionally be thinned to provide the desired transmittance.Additionally or alternatively, the coating 7 can be provided withblocker layers that are deposited as dielectric films (such as oxide,nitride, and/or oxynitride films) throughout their thickness (ratherthan having an innermost metal portion). Here, the coating 7 desirablyprovides a visible transmittance within any one or more of the rangesnoted in this paragraph (or the previous paragraph) in combination withhaving a minimum combined thickness for the three infrared-reflectivefilm regions within any one or more of the ranges described below and/orin combination with any one or more of the minimums noted below for themetal/dielectric ratio.

The use of suboxide protective layers having reduced absorption (e.g.,TiO_(x), where x is less than 2) could even boost the transmission togreater than 0.80.

The term “visible transmittance” is well known in the art and is usedherein in accordance with its well-known meaning. Visible transmittance,as well as visible reflectance, can be determined in accordance withNFRC 300, Standard Test Method for Determining the Solar and InfraredOptical Properties of Glazing Materials and Fading Resistance of Systems(National Fenestration Rating Council Incorporated, adopted December2001, published January 2002). The well-known WINDOW 5.2 a computerprogram can be used in calculating these and other reported opticalproperties.

Preferably, the coated substrate (i.e., the present pane) 12 has aspectral transmission curve with a peak transmission located in thevisible wavelength range. This is readily apparent in FIG. 2. In certainembodiments, this spectral transmission curve has a halfwidth of lessthan 360 nm, less than 320 nm, less than 310 nm, less than 305 nm, lessthan 300 nm, less than 290 nm, less than 280 nm, less than 275 nm, lessthan 265 nm, or even less than 250 nm. In these embodiments, the coating7 provides a highly advantageous narrow transmission curve, whichdesirably has high visible transmittance spanning the visible range and,at the same time, provides an exceptionally steep slope between highlytransmitted visible wavelengths and highly reflected infraredwavelengths. In certain embodiments, the coating 7 additionally (i.e.,together with having any maximum halfwidth noted above) or alternativelyachieves a halfwidth that is greater than 50 nm, greater than 100 nm,greater than 150 nm, or even greater than 175 nm. This can be desirablein providing high levels of visible transmittance over a substantialportion of the visible spectrum.

The present coating 7 provides exceptional efficiency in terms of thelow solar heat gain coefficient that is achieved in combination withhigh visible transmission. The ratio of visible transmittance (as afraction of unity) over SHGC is referred to herein as thevisible-thermal efficiency ratio of the present IG unit 3. This ratiopreferably is greater than 2, greater than 2.2, or even greater than2.3. In some preferred embodiments, this ratio is greater than 2.33,greater than 2.34, greater than 2.37, greater than 2.4, greater than2.42, or even greater than 2.43. In some embodiments, this ratio isabout 2.37. In other embodiments, this ratio is about 2.44. Certainpreferred embodiments (e.g., where the coating 7 is one of the exemplaryfilm stacks tabulated below) provide an IG unit 3 having avisible-thermal efficiency ratio of greater than 2.0 but less than 2.5(e.g., about 2.4-2.5), such as about 2.44.

Another useful parameter to consider is T₇₄₀, i.e., the transmittance at740 nm. The present coating 7 can provide a particularly low T₇₄₀, whileat the same time providing high levels of visible transmittance and goodcolor properties. For example, the present pane 12 preferably has a T₇₄₀of less than 0.30, or even less than 0.20. Perhaps more preferably, thepresent pane 12 (when monolithic, or when part of an insulating unit)has a T₇₄₀ of less than 0.15 (e.g., less than 0.1, less than 0.07, lessthan 0.06, or even less than 0.05). While the desired level oftransmittance at 740 nm can be selected and varied to accommodatedifferent applications, certain preferred embodiments (e.g., where thecoating 7 is one of the exemplary film stacks tabulated below) provide acoated pane 12 (which can be monolithic or part of the IG unit 3) havinga T₇₄₀ of about 0.04.

The present coating 7 can achieve color properties that are exceptional,particularly given the high level of thermal insulation it facilitates.The coating 7 is extremely well suited for applications in whichreflected color is of concern. The following discussion of color isreported using the well-known color coordinates of “a” and “b”. Inparticular, these color coordinates are indicated herein using thesubscript h (i.e., a_(h) and b_(h)) to represent the conventional use ofthe well-known Hunter Lab Color System (Hunter methods/units, Ill. D65,10 degree observer). The present color properties can be determined asspecified in ASTM Method E 308, the entire teachings of which areincorporated herein by reference.

The present IG unit has an exceptionally neutral (i.e., colorless)appearance in reflection, with any appreciable color being of a pleasinghue. The reflected color reported herein is as viewed from the exteriorof the present IG unit (i.e., off the #1 surface side of the outboardpane). In some embodiments, the present IG unit exhibits a reflectedcolor characterized by an a_(h) color coordinate of between about +1.5and about −2 and a b_(h) color coordinate of between about 0 and about−3. These embodiments represent a broader embodiment group wherein(whether or not the a_(h) and b_(h) are within the ranges noted above)the present IG unit has an exterior reflected color characterized by achroma magnitude number (defined as the square root of [a_(h) ²+b_(h)²]) of less than about 3.6. It is a commonly stated goal for coatings toachieve a color neutral appearance. With coatings having three or moreinfrared-reflection film regions, however, this becomes a more difficultpursuit, and the difficulty tends to increase with greater total metalthickness. Moreover, the color properties achieved by the presentcoatings are particularly surprising given the metal/dielectric ratiosused in certain embodiments disclosed herein.

Preferably, the magnitude of at least one of the a_(h) and b_(h)coordinates is negative (in some embodiments, both are negative). Incertain embodiments, at least one these color coordinates (e.g., b_(h))is significantly away (e.g., by at least 0.25, at least 0.3, or at least0.5 in magnitude) from the vertical and/or horizontal axes of the colorspace (i.e., away from the “zero” coordinates). As one approaches thevertical and/or horizontal axes of the color space, a small change inthe magnitude of a_(h) or b_(h) may translate into a considerable changein terms of actual appearance, the less desirable yellow or red zonesbeing thereby encroached.

The present coating 7 can achieve a reflected color that is exceptionalin actual appearance. In certain preferred embodiments (e.g., where thecoating 7 is one of the exemplary film stacks tabulated or detailedbelow), the IG unit exhibits a reflected color characterized by an a_(h)color coordinate of between about +1 and about −1 (e.g., between about 0and about −0.5) and a b_(h) color coordinate of between about −0.5 andabout −2.5 (e.g., between about −1.5 and about −1.75). These embodimentsrepresent a broader group of embodiments wherein (whether or not a_(h)and b_(h) are within the noted ranges) the present IG unit has anexterior reflected color characterized by a chroma magnitude number ofless than about 2.7, such as less than about 1.82. The desirability ofthese color properties on a qualitative level (in terms of theappearance of a window bearing this coating) is best appreciated byviewing an IG unit bearing the present coating 7 in comparison to IGunits bearing other coatings that have comparable total amounts ofinfrared-reflection film.

The present IG unit also exhibits a pleasing transmitted color.Preferably, the IG unit exhibits a transmitted color characterized by ana_(h) color coordinate of between about −3.5 and about −6 and a b_(h)color coordinate of between about +2.25 and about +4.5. In certainpreferred embodiments (e.g., where the coating is one of the preferredfilm stacks tabulated or detailed below), the IG unit exhibits atransmitted color characterized by an a_(h) color coordinate of betweenabout −4 and about −5.5 (e.g., between about −4.5 and about −5) and ab_(h) color coordinate of between about +2.5 and about +4.25 (e.g.,between about +3 and about +3.5). These embodiments represent a broaderembodiment group wherein the magnitude of at least one of the a_(h) andb_(h) coordinates is negative for transmitted color.

FIG. 4 exemplifies certain embodiments that provide a coated substrate12 having a major surface 18 bearing a low-emissivity coating 7. Thecoating includes, in sequence from the major surface 18 outwardly, afirst transparent dielectric film region 20, a first infrared-reflectionfilm region 100, a second transparent dielectric film region 40, asecond infrared-reflection film region 200, a third transparentdielectric film region 60, a third infrared-reflection film region 300,and a fourth transparent dielectric film region 80. In FIG. 4, optionalblocker film regions 105, 205, 305 are shown, although these are notrequired in all embodiments. Also, blocker film regions or nucleationlayers can optionally be provided beneath the infrared-reflection filmregions.

A variety of substrates are suitable for use in the present invention.In most cases, the substrate 12 is a sheet of transparent material(i.e., a transparent sheet). However, the substrate 12 is not requiredto be transparent. For example, opaque substrates may be useful in somecases. It is anticipated, however, that for most applications, thesubstrate will comprise a transparent or translucent material, such asglass or clear plastic. In many cases, the substrate 10 will be a glasspane. A variety of glass types can be used, and soda-lime glass isexpected to be preferred.

Substrates of various sizes can be used in the present invention.Commonly, large-area substrates are used. Certain embodiments involve asubstrate 12 having a major dimension (e.g., a width or length) of atleast about 0.5 meter, preferably at least about 1 meter, perhaps morepreferably at least about 1.5 meters (e.g., between about 2 meters andabout 4 meters), and in some cases greater than 2 meters or at leastabout 3 meters.

Substrates of various thicknesses can be used in the present invention.

Commonly, substrates with a thickness of about 1-5 mm are used. Someembodiments involve a substrate 10 with a thickness of between about 2.3mm and about 4.8 mm, and perhaps more preferably between about 2.5 mmand about 4.8 mm. In some cases, a sheet of glass (e.g., soda-limeglass) with a thickness of about 3 mm is used.

The present coating includes at least two optical cavities. For purposesof the present disclosure, the term “cavity” is defined to mean theregion (which is occupied by film) between two adjacentinfrared-reflection film regions. In some of the present embodiments,the coating has only two cavities. In other embodiments, the coating hasthree or more cavities. In some of the both embodiment types, each ofthe cavities has a thickness of between about 300 Å and about 850 Å, andperhaps more preferably between about 400 Å and about 750 Å.

Some embodiments of the invention provide a metal/dielectric ratio thathas surprisingly been found to give exceptional results. Here, the“metal/dielectric ratio” is the total thickness of all theinfrared-reflection film regions (in embodiments involving silver, thetotal silver thickness) divided by the total thickness of thetransparent dielectric film regions (not counting any metallic blockerlayers that may be present). In the present embodiments, themetal/dielectric ratio preferably is at least 0.2, at least 0.22, atleast 0.25, at least 0.26, or even at least 0.27. Tabulated below areexemplary embodiments wherein this ratio is between about 0.27 and about0.28.

Each infrared-reflection film region 100, 200, 300 can advantageouslycomprise (optionally at least 50 atomic percent of, in some casesconsisting essentially of) silver. Further, in some embodiments, thethickness of at least one of the infrared-reflection film regions 100,200, 300 is greater than 150 angstroms, greater than 175 angstroms, oreven greater than 200 angstroms. Additionally or alternatively, thefirst, second, and third infrared-reflection film regions can optionallyhave a combined thickness of greater than 425 Å, greater than 450 Å,greater than 460 Å, greater than 470 Å, greater than 475 Å, or evengreater than 485 Å. In one embodiment, this combined thicknesses isabout 477 Å. For example, in some cases, the first, second, and thirdinfrared-reflection film regions 100, 200, 300 are silver layers havingrespective thicknesses of 122 Å, 149 Å, and 206 Å. In anotherembodiment, the combined thicknesses is about 492 Å. For example, insome cases, the first, second, and third infrared-reflection filmregions 100, 200, 300 are silver layers having respective thicknesses of128 Å, 157 Å, and 207 Å.

Certain embodiments provide the second and third infrared-reflectionfilm regions (each of which can optionally be a layer, such as adiscrete layer of silver) at a combined thickness of at least 325 Å, atleast 335 Å, at least 340 Å, at least 350 Å, or even at least 355 Å. Insome embodiments, this combined thickness is 355-395 Å. Here, arelatively large amount of reflective film (e.g., silver) isconcentrated at the outer portions of the coating, with the goal of thishaving a particularly great lowering of emissivity while at the sametime facilitating particularly good color, visible transmission, andvisible reflection properties. Additionally or alternatively, at leastone of the infrared-reflection film regions can be thicker than at leastone of the other infrared-reflection film regions by at least 50 Å, atleast 75 Å, or at least 80 Å. In some preferred embodiments of thisnature, it is the third infrared-reflection film region that is thickerthan the first infrared-reflection film region, by one or more of thenoted amounts.

Some embodiments provide an arrangement wherein the secondinfrared-reflection film region is thicker than the firstinfrared-reflection film region by at least 10 Å, at least 20 Å, atleast 25 Å, or even at least 30 Å. Additionally or alternatively, thethird infrared-reflection film region can be thicker than the secondinfrared-reflection film region by at least 25 Å, at least 35 Å, atleast 40 Å, or even at least 50 Å.

Thus, certain embodiments provide a third infrared-reflection filmregion at a greater thickness than a second infrared-reflection filmregion, while the second infrared-reflection film region has a greaterthickness than a first infrared-reflection film region. Related methodsinvolve a first power level being used to sputter a silver-containingtarget in depositing the first infrared-reflective film region, a secondpower level being used to sputter a silver-containing target indepositing the second infrared-reflective film region, and a third powerlevel being used to sputter a silver-containing target in depositing thethird infrared-reflective film region. Here, the third power level canadvantageously be greater than the second power level, while the secondpower level is greater than the first power level.

One group of embodiments provides a coated substrate (e.g., a coatedpane, such as a glass pane, optionally having a major dimension of atleast 1 meter, or at least 1.2 meters) bearing a low-emissivity coating7 that comprises three infrared-reflection film regions 100, 200, 300having a combined thickness of between 420 Å and 575 Å, optionally incombination with a metal/dielectric ratio within one or more of theranges described above.

The infrared-reflection film regions 100, 200, 300 are described belowin further detail. Briefly, though, some preferred embodiments providethese film regions in the form of silver layers each comprising(optionally consisting essentially of) silver, with these three layersoptionally being the only silver-containing layers in the coating.

To optimize the conductivity and crystallinity of the metal (e.g., Ag)films, a surface treatment can optionally be applied to improve theproperties (e.g., surface energy) of the growth control layer.

Three silver-containing layers can optionally each have a thickness ofbetween about 50 Å and about 300 Å. Preferably, though, they each have athickness of between about 75 Å and about 275 Å, and perhaps morepreferably between about 100 Å and about 250 Å. In one embodiment ofthis nature, the substrate 12 is a glass sheet having a major dimensionof at least one meter (or at least 1.2 meters, optionally greater than 2meters), and this glass sheet is part of a multiple-pane insulatingglass unit that includes at least one other glass sheet, where themultiple-pane unit has a between-pane space 1500, which can optionallybe evacuated, filled with air, or filled with air and insulative gas(e.g., argon).

With respect to the four transparent dielectric film regions 20, 40, 60,80, in certain embodiments, each of these film regions has a totalphysical thickness of between about 50 Å and about 900 Å, and perhapsmore preferably between about 100 Å and about 800 Å. These dielectricfilm regions are described below in more detail.

The first transparent dielectric film region 20 is applied over (in somecases, directly over) a major surface 18 of the substrate 12. This filmregion 20 can be of any composition that includes at least some (or,optionally, consists essentially of) transparent dielectric film. Insome cases, the first transparent dielectric film region 20 is a singlelayer. In other cases, it comprises a plurality of layers. As describedin U.S. Pat. No. 5,296,302 (the teachings of which concerning usefuldielectric materials are incorporated herein by reference), usefuldielectric film materials for this purpose include oxides of zinc, tin,indium, bismuth, titanium, hafnium, zirconium, and alloys thereof. Filmcomprising silicon nitride and/or silicon oxynitride is also used insome embodiments. The film region 20 can optionally include one or moreabsorbing dielectric and/or metal films, such as to control shading,color, or other optical properties.

The first transparent dielectric film region 20 can be a single layer ofa single dielectric material. If a single layer is used, it is generallypreferred that this inner dielectric layer be formed of a mixture ofzinc oxide and tin oxide (referred to below, e.g., in Table 1, as“Zn+O”). It should be understood, though, that such a single layer canbe replaced with two or more layers of different dielectric materials.

In certain embodiments, each of the first, second, and third (countingfrom substrate) dielectric regions (or “optical cavities”) comprises anuppermost (i.e., further from the substrate) oxide layer in contact witha Ag layer, and such uppermost layer has a composition of Zn+ where plusdenominates a concentration x by weight of a desired metal like: Sn, In,Ni, Cr, Mo with 0<X<0.3. This refers to the ratio of the weight, on ametal-only basis, of the desired metal over the total weight of allmetals in the Zn+ film (in some cases, this ratio is the Sn weightdivided by the total weight of Sn and Zn, such as where the layer iszinc tin oxide). Such a top layer has preferentially a thickness of atleast 2.5 nm and less than 5.0 nm. The remainder of the cavity layer, insome cases, comprises film having higher refractive index, such astitania (e.g., TiO₂) or niobium oxide.

In certain embodiments, the first transparent dielectric film region 20comprises a graded thickness of film, having a composition that changes(e.g., in a gradual manner) with increasing distance from the substrate12.

In some particular embodiments, the first transparent dielectric filmregion 20 comprises film (optionally comprising zinc oxide, such as azinc tin oxide) having a refractive index of 1.7 or greater. Forexample, between the first infrared-reflection film region 100 and thesurface 18 of the substrate 12, there can advantageously be provided adesired total thickness of film that has a refractive index of 1.7 orgreater. In some cases, this desired total thickness is less than 195angstroms, less than 190 angstroms, less than 175 angstroms, less than165 angstroms, less than 145 angstroms, or even less than 140 angstroms.Some related method embodiments involve depositing no more than 175angstroms of transparent dielectric film between a firstinfrared-reflection film region 100 and a top major surface of a glasssheet.

Referring again to FIG. 4, the first infrared-reflection film region isidentified by the reference number 100. This film region 100 preferablyis contiguous to, i.e., in direct physical contact with, the outer faceof the first transparent dielectric film region 20. Any suitableinfrared reflection material can be used. Silver, gold, and copper, aswell as alloys thereof, are the most commonly used infrared-reflectionfilm materials. Preferably, the infrared-reflection film consistsessentially of silver or silver combined with no more than about 5% ofanother metal, such as another metal selected from the group consistingof nickel, molybdenum, tantalum, platinum, and palladium. This, however,is by no means required.

When desired for protection of the infrared-reflection film duringapplication of subsequent film and/or during any heat treatment (e.g.,tempering), a first blocker film region 105 can optionally be providedover and contiguous to the first infrared-reflection film region 100.This blocker film region 105 can be provided to protect the underlyinginfrared-reflection film region 100 from plasma chemical attack. In suchcases, any material that is readily oxidized may be useful. In certainembodiments, a thin layer of titanium metal is applied, and in somecases (e.g., cases where oxide film is reactively deposited directlyover such a blocker film region) at least an outermost thickness of thattitanium metal is converted to titanium oxide of varying stoichiometryduring deposition of overlying film. In another embodiment, the blockerfilm region 105 is deposited as a layer of niobium. Useful blockerlayers comprising niobium are discussed in detail in PCT InternationalPublication No. WO 97/48649. The teachings of this PCT Publicationrelating to blocker layers are incorporated herein by reference. Inother embodiments, the blocker film region 105 can comprise a materialselected from the group consisting of nickel, chromium, zinc, tin,aluminum, indium, and zirconium.

In some embodiments, a high transmission blocker layer material (e.g., adielectric material, optionally as deposited) is used for one or more(optionally for each of the) blocker film regions 105, 205, 305. Thematerial used, for example, can be an oxide, nitride, or oxynitride.This material can advantageously be sputtered from a ceramic targeteither in an inert atmosphere, a nitriding atmosphere, or a slightlyoxidizing atmosphere. In some embodiments, a substoichiometricsputterable target material is used. For example, the target materialcan optionally comprise substoichiometric titania, TiO_(x), where x isless than 2. Alternatively, a ZnAlO target may be used. In still otherembodiments, a ceramic target comprising titanium, silicon, and oxygenis used. If so desired, a very thin metal film (e.g., less than 25 Å,less than 20 Å, less than 15 Å, less than 10 Å, less than 9 Å, or evenless than 8 Å) can be applied directly over the infrared-reflectionfilm, and directly over this thin metal film there can be applied adielectric blocker film region (which optionally has a thickness of lessthan 50 Å, less than 40 Å, less than 30 Å, less than 25 Å, less than 20Å, or even less than 15 Å). When provided, the very thin metal film can,for example, be deposited as a metallic film comprising titanium,niobium, nickel, chromium, nickel-chrome, zinc, tin, zinc-tin, aluminum,indium, zirconium, or a combination including at least one of thesematerials together with one or more other metallic materials. In theseembodiments, the thin metal film desirably is deposited in an inertatmosphere and the dielectric blocker film region can be depositedeither in an inert or reactive atmosphere. For example, when sputteringis used, a ceramic target can be sputtered in an inert or slightlyreactive atmosphere, or a metal target can be sputtered in a reactiveatmosphere.

In one particular group of embodiments, the coating 7 comprises threeinfrared-reflection film regions directly over at least one of which(and optionally over each of which) there is provided a blocker filmregion that is deposited in a non-metallic form (e.g., as a non-metallicmaterial selected from the group consisting of an oxide, a nitride, andan oxynitride, including substoichiometric forms thereof). In this groupof embodiments, the thickness of each such blocker film region can bewithin any one of the ranges noted herein for the optional blocker filmregions, such as less than 50 Å. In some cases, the optional blockerfilm region has a thickness in the range of 3-35 Å, 3-25 Å, or 3-18 Å.

In certain embodiments, the first blocker film region 105 has aparticularly small thickness, such as less than 25 Å, less than 20 Å,less than 15 Å, less than 10 Å, less than 7 Å, less than 6 Å, or evenless than 5 Å. While not shown in FIG. 4, a blocker film region canoptionally be provided under the first infrared-reflection film region100 as well.

In certain embodiments, the blocker regions can comprise two or moresublayers. In some cases, a first sublayer is provided directlycontacting the infrared-reflection film and a second sublayer provideddirectly over the first sub-layer. The first sublayer can be a materialreacted to a less degree (e.g., sputtered metal layer) and the secondsublayer can be a material reacted to a higher degree (e.g., asubstoichiometric layer). The second sub-layer can have less absorptionthan the material of the first sub-layer. Such an arrangement can helpto keep the optical absorption low and also helps to prevent the sheetresistance of the infrared-reflective film from increasing. In suchcases, the combined thickness of the sublayers can be up to 100 Å.

The second transparent dielectric film region 40 is positioned betweenthe first infrared-reflection film region 100 and the secondinfrared-reflection film region 200 (the area between these two filmregions 100, 200 being referred to herein as the “first cavity”). Thefilm region 40 can be referred to as a first “spacer” film region, whichis located in the first cavity. This first spacer film region 40 can bea single layer of a single transparent dielectric material, or it can bea plurality of layers of different transparent dielectric materials. Insome cases, the second transparent dielectric film region 40 comprisesat least three transparent dielectric layers. Optionally, there are atleast five, or even at least seven, such layers. As an alternative tousing one or more discrete layers, part or all of the second transparentdielectric film region 40 can have a graded composition (optionallycharacterized by a gradual transition from one transparent dielectricmaterial to another with increasing distance from the substrate). Thefilm region 40 can optionally include one or more absorbing dielectricand/or metal films, such as to control shading, color, or other opticalproperties.

The next illustrated film region is the second infrared-reflection filmregion 200. This film region 200 preferably is contiguous to the outerface of the second transparent dielectric film region 40. Any suitableinfrared reflection material can be used, such as silver, gold, andcopper, or alloys including one or more of these metals. In someparticular embodiments, the infrared-reflection film consistsessentially of silver or silver combined with no more than about 5% ofanother metal, such as another metal selected from the group consistingof gold, platinum, and palladium.

When desired for protection of the second infrared-reflection filmregion 200, a second blocker film region 205 can optionally be providedover and contiguous to the second infrared-reflection film region 200.This blocker film region 205, for example, can comprise any materialthat is readily oxidized. In certain embodiments, a thin layer oftitanium metal is applied, and in some cases (e.g., cases where oxidefilm is reactively deposited directly over this blocker film region 205)at least an outermost thickness of that titanium metal is converted to atitanium oxide of varying stoichiometry during deposition of overlyingfilm. In other cases, the blocker film region 205 can comprise amaterial selected from the group consisting of nickel, chromium, zinc,tin, aluminum, indium, and zirconium. In another embodiment, the blockerfilm region 205 is deposited as a layer of niobium or one of thenon-metallic blocker film materials discussed above. The blocker filmregion 205, for example, can optionally comprise the above-notedarrangement of: a very thin metal film directly over film region 200,and; a dielectric film directly over this very thin metal film.Alternatively, the dielectric film can be deposited directly over filmregion 200.

Suitable thicknesses for the optional second blocker film region 205generally range from 3-35 Å, 3-25 Å, or 3-18 Å. In certain embodiments,the second blocker film region 205 has a particularly small thickness,such as less than 25 Å, less than 20 Å, less than 15 Å, less than 10 Å,less than 7 Å, less than 6 Å, or even less than 5 Å. While not shown inFIG. 4, a blocker film region can optionally be provided under thesecond infrared-reflection film region 200.

The third transparent dielectric film region 60 is positioned betweenthe second infrared-reflection film region 200 and the thirdinfrared-reflection film region 300. This transparent dielectric filmregion 60 is also a spacer film region (it is located within the “secondcavity”), and can be referred to as the second spacer film region. Thethird transparent dielectric film region 60 can be a single layer of asingle transparent dielectric material, or it can be a plurality oflayers of different transparent dielectric materials. In some cases, thethird transparent dielectric film region 60 comprises at least threetransparent dielectric layers. Optionally, there are at least five, oreven at least seven, such layers. As an alternative to one or morediscrete layers, part or all of the third transparent dielectric filmregion 60 can have a graded composition. The film region 60 canoptionally include one or more absorbing dielectric (TiN, Ti oxynitrides, etc.) and/or metal films, such as to control shading, color,or other optical properties.

The next illustrated film region is the third infrared-reflection filmregion 300. This film region 300 preferably is contiguous to the outerface of the third transparent dielectric film region 60. Any suitableinfrared reflection material can be used (e.g., silver, gold, copper, oran alloy comprising one or more of these metals). In some particularembodiments, the third infrared-reflection film region 300 consistsessentially of silver or silver combined with no more than about 5% ofanother metal, such as another metal selected from the group consistingof gold, platinum, and palladium.

When desired for protection of the third infrared-reflection film region300, a third blocker film region 305 can optionally be provided over andcontiguous to the third infrared-reflection film region 300. Thisblocker film region 305, for example, can comprise any material that isreadily oxidized. In certain embodiments, a thin layer of titanium metalis applied, and in some cases (e.g., cases where oxide film isreactively deposited directly over this blocker film region 305) atleast an outermost thickness of that titanium metal is converted to atitanium oxide of varying stoichiometry during deposition of overlyingfilm. In other cases, the blocker film region 305 can comprise amaterial selected from the group consisting of nickel, chromium, zinc,tin, aluminum, indium, and zirconium. In another embodiment, the blockerfilm region 305 is deposited as a layer of niobium or one of thenon-metallic blocker film materials described above. The blocker filmregion 305, for example, can optionally comprise the above-notedarrangement of: a very thin metal film directly over film region 300,and; a dielectric film directly over this very thin metal film.Alternatively, the dielectric film can be deposited directly over thefilm region 300.

Suitable thicknesses for the optional third blocker film region 305generally range from 3-35 Å, 3-25 Å, or 3-18 Å. In certain embodiments,the third blocker film region 305 has a particularly small thickness,such as less than 25 Å, less than 20 Å, less than 15 Å, less than 10 Å,less than 7 Å, less than 6 Å, or even less than 5 Å. While not shown inFIG. 4, a blocker film region can optionally be provided under the thirdinfrared-reflection film region 300 as well.

Given the large number of blocker film regions provided in certainembodiments, it can be advantageous to use a very small thickness forone or more of the blocker film regions. Thus, in some embodiments,directly over at least one of the infrared-reflection film regions thereis provided a blocker film region having a thickness of less than 20 Å,less than 15 Å, less than 7 Å, less than 6 Å, or even less than 5 Å.Further, in some embodiments, the coating 7 includes three blocker filmregions 105, 205, 305, and the combined thickness of all three of theseblocker film regions is less than less than 60 Å, less than 45 Å, lessthan 30 Å, less than 25 Å, less than 20 Å, less than 18 Å, or even lessthan 15 Å.

Moreover, certain embodiments provide the coating with a high combinedthickness for the three infrared-reflection film regions (e.g., anycombined thickness range noted herein) in combination with one or more(e.g., three) blocker film regions 105, 205, 305 of the dielectric orthin metal/dielectric type described above. These embodiments canprovide an exceptional combination of good thermal insulating propertiesand high visible transmission.

The fourth transparent dielectric film region 80 (which may, though neednot, be an outer coat) is located further from the substrate 12 than thethird infrared-reflection film region 300. In some, though not all,embodiments, this film region 80 defines the coating's outermost face 77(which face can optionally be exposed, i.e., not covered by any otherfilm). The fourth transparent dielectric film region 80 can be a singlelayer of a single transparent dielectric material, or it can be aplurality of layers of different transparent dielectric materials. Insome cases, the fourth transparent dielectric film region 80 comprisesat least three transparent dielectric layers. Optionally, there are atleast five, or even at least seven, such layers. As an alternative tousing one or more discrete layers, part or all of the fourth transparentdielectric film region 80 can have a graded composition. The film region80 can optionally include one or more absorbing dielectric and/or metalfilms, such as to control shading, color, or other optical properties.

Thus, it can be appreciated that the present coating 7 desirablyincludes at least four transparent dielectric film regions 20, 40, 60,80. In some embodiments, the coating 7 comprises one or more, two(wherein optionally an infrared-reflection film region is locatedbetween, though not in contact with, such two nitride films) or more, orthree or more nitride or oxynitride films, such as at least one, atleast two, or at least three films comprising silicon nitride and/orsilicon oxynitride. In some embodiments of this nature, the coating 7includes at least one nitride or oxynitride film (optionally comprisingsilicon nitride and/or silicon oxynitride) having a thickness of lessthan 150 angstroms, less than 140 angstroms, or even less than 125angstroms (this type of convention globally meaning greater than zero),together with at least one other nitride or oxynitride film (optionallycomprising silicon nitride and/or silicon oxynitride) having a thicknessof greater than 50 angstroms, greater than 75 angstroms, greater than100 angstroms, greater than 150 angstroms, or even greater than 175angstroms. In some cases, the latter noted film is located eitherbetween the first 100 and second 200 infrared-reflection film regions orbetween the second 200 and third 300 infrared-reflection film regions.That is, it forms (or is part of) one of the spacer film regions.Desirably, the outermost film of the coating 7 comprises siliconnitride, as described in the exemplary method detailed below. In oneembodiment, the coating includes two nitride films: one in an outer coatformed by film region 80 and one in film region 60.

The total thickness of the present coating 7 can be varied to suit therequirements of different applications. In certain preferredembodiments, the total physical thickness of the coating 7 is greaterthan 1,750 angstroms, greater than 1,800 angstroms, greater than 1,900angstroms, or even greater than 2,000 angstroms. For any embodimentdisclosed in this specification, the coating's total thickness canoptionally fall within any one or more of the ranges specified in thisparagraph.

In one particular group of embodiments, the thickness of the thirdinfrared-reflection film region 300 is greater than the thickness of thesecond infrared-reflection film region 200, and the thickness of thesecond infrared-reflection film region 200 is greater than the thicknessof the first infrared-reflection film region 100. This group ofembodiments is advantageous in terms of providing good reflected colorproperties. In one subgroup of these embodiments, the first 100, second200, and third 300 infrared-reflection film regions each comprise (orconsist essentially of) silver. Optionally, the coating 7 also has ametal/dielectric ratio within one or more of the ranges described above.

For purposes of the present specification, the first reflection-regionratio is defined as being the thickness of the first infrared-reflectionfilm region 100 over the thickness of the second infrared-reflectionfilm region 200, and the second reflection-region ratio is defined asbeing the thickness of the second infrared-reflection film region 200over the thickness of the third infrared-reflection film region 300. Insome particular embodiments, at least one of the first and secondreflection-region ratios is less than 0.85, less than 0.83, or even lessthan 0.80. Optionally, the first and second reflection-region ratios areboth less than 0.83, such as about 0.819 and 0.723 respectively.

In some embodiments of the present group, the thickness of at least oneof the infrared-reflection film regions 100, 200, 300 is greater than150 Å, greater than 175 Å, or even greater than 200 Å. Additionally oralternatively, the first, second, and third infrared-reflection filmregions can optionally have a combined thickness of greater than 425 Å,greater than 450 Å, greater than 460 Å, greater than 475 Å, or evengreater than 485 Å. In certain embodiments, this combined thickness isabout 477 Å. For example, in some cases, the first, second, and thirdinfrared-reflection film regions 100, 200, 300 are silver layers havingrespective thicknesses of 122 Å, 149 Å, and 206 Å. In other embodiments,the combined thickness is about 492 Å. For example, in some cases, thefirst, second, and third infrared-reflection film regions 100, 200, 300are silver layers having respective thicknesses of 128 Å, 157 Å, and 207Å.

In some embodiments of the present group, the first transparentdielectric film region 20 comprises film (optionally comprising zincoxide, such as a zinc tin oxide) having a refractive index of 1.7 orgreater. For example, between the first infrared-reflection film region100 and the surface 18 of the substrate 12, there can advantageously beprovided a desired total thickness of film that has a refractive indexof 1.7 or greater. In certain embodiments, this desired total thicknessis less than 195 angstroms, less than 190 angstroms, less than 175angstroms, less than 165 angstroms, less than 145 angstroms, or evenless than 140 angstroms.

For purposes of this disclosure, the primary dielectric-region ratio isdefined as being the thickness of the first transparent dielectric filmregion 20 over the thickness of the fourth transparent dielectric filmregion 80. This ratio can advantageously be less than 0.75, or even lessthan 0.6, while at the same time optionally being greater than 0.34,greater than 0.35, greater than 0.37, or even greater than 0.40. In oneexemplary embodiment, this ratio is about 0.47. A primarydielectric-region ratio within any one or more of these ranges canoptionally be adopted for any embodiment of the present group, or forany other embodiment disclosed in this specification (e.g., incombination with one or more of the optional ranges noted for themetal/dielectric ratio).

Certain embodiments of the invention provide a particular ratio for thecombined thickness of the first transparent dielectric film region 20(which may be the base coat, i.e., the dielectric film region closest tothe substrate) and the fourth transparent dielectric film region 80(which may be the outer coat) divided by the combined thickness of thesecond 40 and third 60 transparent dielectric film regions (which may bethe first and second spacer layers, respectively). In these embodiments,this ratio preferably is greater than about 0.43, greater than about0.45, or even greater than about 0.475. Coatings having this arrangementof dielectric thickness have been found to facilitate excellentproperties, including good color, high visible transmission, etc., evenwhen large amounts of infrared-reflection film is used.

Table 1 below shows one exemplary film stack that can be used as thepresent coating 7:

TABLE 1 FILM STACK A Glass TiO2 132 Å Ag 122 Å Ti  20 Å TiO2 468 Å Ag149 Å Ti  20 Å TiO2 546 Å Ag 206 Å Ti  20 Å TiO2 280 Å

Table 2 below illustrates three more exemplary film stacks that can beused as the present coating 7:

TABLE 2 FILM STACK B STACK C STACK D Glass Glass Glass Glass SnO2 165 Å164 Å 164 Å Ag 117 Å 117 Å 117 Å Ti  20 Å  20 Å  30 Å SnO2 591 Å 592 Å591 Å Ag 154 Å 147 Å 154 Å Ti  20 Å  20 Å  35 Å SnO2 665 Å 665 Å 665 ÅAg 206 Å 208 Å 206 Å Ti  20 Å  20 Å  35 Å SnO2 314 Å 314 Å 310 Å

Table 3 below illustrates a further exemplary film stack that can beused, perhaps as a temperable coating, as the present coating 7. Here,the coating is representative of a class of embodiments wherein a triplesilver coating is provided with at least about 50 angstroms (such asabout 100 Å) of film comprising silicon dioxide directly on thesubstrate.

TABLE 3 FILM THICKNESS Glass SiO2 >50 Å Zn + O 164 Å Ag 130 Å Ti  35 ÅZn + O 599 Å Ag 165 Å Ti  35 Å Zn + O 667 Å Ag 218 Å Ti  35 Å Zn + O 313Å

Table 4 below illustrates another exemplary film stack that can be used,perhaps as a temperable coating, as the present coating 7:

TABLE 4 FILM THICKNESS Glass SiO2 >50 Å Zn + O 165 Å Ag 135 Å Ti  35 ÅZn + O 626 Å Ag 171 Å Ti  35 Å Zn + O 693 Å Ag 225 Å Ti  35 Å Zn + O 319Å

Table 4 is representative of a class of embodiments wherein alow-emissivity coating includes three infrared-reflective films having acombined thickness of at least about 525 angstroms. In addition, theoutermost two infrared-reflective films in such embodiments canoptionally have a combined thickness of at least about 385 angstroms.

FIG. 5 schematically depicts a multiple-pane insulating glazing unitbearing a multiple cavity low-emissivity coating in accordance withcertain embodiments of the invention. Here, the multiple cavitylow-emissivity coating 7 is on the #2 surface of the IG unit 3, and the#1 surface is exposed to an outdoor environment. The IG unit hereincludes a spacer 130 adhered between the two panes 12, 12′ by twodeposits of sealant 1700, 1800. The spacer can alternatively be anintegral part of a sash, frame, etc. Moreover, a single deposit ofsealant can alternatively be used. In embodiments of this nature, the IGunit preferably is mounted on a sash and/or frame that maintains the IGunit in the illustrated/noted configuration.

Methods for depositing films onto a sheet-like substrate are alsoprovided. In accordance with the present methods, a substrate 12 havinga surface (e.g., a major surface) 18 is provided. If desired, thissurface 18 can be prepared by suitable washing or chemical preparation.The present coating 7 is deposited on the surface 18 of the substrate12, e.g., as a series of discrete layers, as a thickness of graded film,or as a combination including at least one discrete layer and at leastone thickness of graded film. The coating can be deposited using anysuitable thin film deposition technique. One preferred method ismagnetron sputtering, which is commonly used in industry. Reference ismade to Chapin's U.S. Pat. No. 4,166,018, the teachings of which areincorporated herein by reference. Thus, the present methods can involvesequentially depositing the film regions of any coating embodimentdisclosed herein by any one or more thin film deposition techniques. Onewell known method is magnetron sputtering.

Briefly, magnetron sputtering involves transporting a substrate througha series of low pressure zones (or “chambers” or “bays”) in which thevarious film regions that make up the coating are sequentially applied.Metallic film is sputtered from metallic sources or “targets,” typicallyin an inert atmosphere such as argon. To deposit dielectric film, thetarget may be formed of the dielectric itself (e.g., zinc aluminum oxideor titanium oxide, optionally substoichiometric titania). In othercases, the dielectric film is applied by sputtering a metal target in areactive atmosphere. To deposit zinc oxide, for example, a zinc targetcan be sputtered in an oxidizing atmosphere; silicon nitride can bedeposited by sputtering a silicon target (which may be doped withaluminum or the like to improve conductivity) in a reactive atmospherecontaining nitrogen gas. The thickness of the deposited film can becontrolled by varying the speed of the substrate and/or by varying thepower on the targets. The low-emissivity coating including (optionallyhaving only) three infrared-reflective films can optionally have atleast one of its films deposited by sputtering.

Another method for depositing thin film on a substrate involves plasmachemical vapor deposition. Reference is made to U.S. Pat. No. 4,619,729(Johncock et al.) and U.S. Pat. No. 4,737,379 (Hudgens et al.), theteachings of both of which concerning CVD techniques are incorporatedherein by reference. Such plasma chemical vapor deposition involves thedecomposition of gaseous sources via a plasma and subsequent filmformation onto solid surfaces, such as glass substrates. The filmthickness can be adjusted by varying the speed of the substrate as itpasses through a plasma zone and/or by varying the power and/or gas flowrate within each zone.

In certain embodiments, the low-emissivity coating is deposited in acoater having a series of sequentially connected sputtering chambers.The chambers preferably are vacuum deposition chambers in whichcontrolled environments can be established. In some cases, each chamberis adapted for use at (e.g., is adapted for establishing and maintainingtherein) a total gas pressure of less than about 140 torr., morepreferably less than about 0.1 torr., and perhaps most commonly betweenabout 1 mtorr. and about 0.1 torr. (e.g., between about 1 mtorr. andabout 30 mtorr.). Thus, the coater preferably has gas delivery andpumping systems adapted for establishing and maintaining pressureswithin any range or ranges described in this paragraph.

Some embodiments involve a coater having more than 36 sputteringchambers (or “bays”), at least 40 chambers, at least 45 chambers, or atleast 50 chambers (such as more than 52, at least 55, more than 56, atleast 60, at least 63, or at least 65). In these embodiments, the largenumber of deposition chambers allows an incredibly wide variety ofcoatings to be manufactured with a single coater. Particularly complexcoatings can also be deposited in a single pass of the substrate throughthe coater. In preferred embodiments, a low-emissivity coating havingthree infrared-reflective layers is deposited in a single pass of thesubstrate through the coater. Preferably, the single pass of thesubstrate is continuous, so the coating process is not interrupted bystopping the substrate, or removing the substrate from the coater,during the single pass. In many cases, the single pass of the substratethrough the coater is carried out by moving the glass sheetsubstantially linearly in a substantially constant direction. Thesubstrate can optionally be moved at a substantially constant rate ofspeed throughout the entirety of the single pass.

In some embodiments, the coater has a large number of downwardsputtering chambers. For example, the coater can optionally include atleast 36 downward sputtering chambers, at least 39 downward sputteringchambers, at least 42 downward sputtering chambers, or at least 45downward sputtering chambers. Reference is made to FIG. 9. Here, thecoater has at least 36 chambers adapted for downward sputtering. In FIG.13, the coater has at least 45 chambers adapted for downward sputtering.Coaters of this nature provide a number of benefits. For example, theyallow particularly thick and/or complex coatings to be deposited bydownward sputtering, and these coatings therefore need not contact thetransport rollers on which the substrates are conveyed. Particularlythick and/or complex coatings may be more likely (in comparison tothinner and/or more simple coatings) to show visible traces of contactor other undesirable damage from transport rollers or other substratesupports.

In the foregoing embodiments, each downward sputtering chamber may beadapted for downward-only sputtering, or for dual-direction sputtering.FIG. 11 shows 30 downward sputtering chambers C1-C30 adapted fordownward-only sputtering, and six downward sputtering chambers C31-C36adapted for dual-direction sputtering. FIG. 13 shows 45 downwardsputtering chambers C1-C45 adapted for downward-only sputtering, and 18downward sputtering chambers C46-C63 adapted for dual-directionsputtering.

FIGS. 10 and 13 exemplify certain method and equipment embodimentsinvolving a coater with an upward sputtering section and a downwardsputtering section. The upward sputtering section is characterized by aseries of lower targets at a lower elevation than the path of substratetravel, while the downward sputtering section is characterized by aseries of upper targets at a higher elevation than the path of substratetravel. In some of these embodiments, the downward sputtering sectionincludes at least 36, at least 39, at least 42, or at least 45 chambersadapted for downward-only sputtering. Additionally or alternatively, theupward sputtering section can optionally include at least 9, at least18, or at least 21 chambers adapted for upward-only sputtering. In somecases, the coater has more than twice as many chambers adapted fordownward sputtering (including downward-only sputtering anddual-direction sputtering) as chambers adapted for upward sputtering(including upward-only sputtering and dual-direction sputtering). Thesecoaters can be used advantageously, for example, to deposit relativelythin and/or less complex coatings on the bottoms of substrates.

In some embodiments involving a coater with an upward sputtering sectionand a downward sputtering section, oxidizing sputtering atmospheres aremaintained in all active chambers of the upward sputtering section, andnitriding sputtering atmospheres are maintained in a plurality of thechambers of the downward sputtering section. Related method embodimentscomprise reactively sputtering all the active lower targets upwardly inoxidizing gas and reactively sputtering a plurality of the upper targetsdownwardly in nitriding gas. These methods, for example, can involvedepositing a coating consisting essentially of oxide film(s) on thebottom of a glass sheet, and depositing a coating comprising a pluralityof nitride films on the top of the glass sheet.

Generally, the substrate is conveyed through the coater at a speed inthe range of about 100-500 inches per minute. Desirably, the substrateis conveyed at a rate exceeding 200 inches per minute, such as greaterthan 250 inches per minute, greater than 275 inches per minute, 300inches per minute or faster, greater than 300 inches per minute, 310inches per minute or faster, greater than 310 inches per minute, orgreater than 325 inches per minute. If desired, the process can beadapted to employ a conveyance rate of 400 inches per minute or faster,greater than 500 inches per minute, 510 inches per minute or faster, or525 inches per minute or faster.

Some embodiments involve depositing a triple-silver low-emissivitycoating using a substrate conveyance rate exceeding 275 inches perminute, perhaps more preferably 300 inches per minute or faster, or 310inches per minute or faster. It is surmised that high conveyance rates,surprisingly, can facilitate improved coating quality, and that theimprovement becomes acute for triple-silver low-emissivity coatings. Forexample, it is surmised that high conveyance rate sputtering of silverat high power levels yields higher quality, perhaps less oxidized,silver film. Thus, the present invention provides embodiments wherein acoating with a particularly large total thickness of silver (or anotherinfrared-reflective metal), such as a triple-silver low-emissivitycoating, is deposited at a high conveyance rate, preferably using asputtering process that involves high power level sputter deposition ofthe silver or other reflective metal. Accordingly, some embodimentsinvolve a combination of using a high conveyance rate and depositing alarge total thickness of silver and/or other infrared-reflectivemetal(s).

One particular embodiment group involves a coating with threeinfrared-reflective film regions deposited by sputteringsilver-containing targets at an average power level exceeding 8.5 kW, orexceeding 9 kW. In some cases, at least one of these silver-containingtargets is sputtered at a power level exceeding 12 kW. Exemplaryembodiments are described below in connection with Table 5.

As discussed above, the coater preferably comprises a series ofconnected chambers (e.g., a line of connected deposition chamber, i.e.,a “coating line”). Such a coating line may comprise a series of chambersaligned and connected so that a substrate (preferably a plurality ofspaced-apart sheet-like substrates, e.g., glass sheets) supported onspaced-apart transport rollers can be conveyed through the chambers ofthe line sequentially. Preferably, the coating line includes narrowevacuated tunnels, which connect adjacent chambers, through whichhorizontally-oriented substrates are conveyed from one chamber to thenext. During film deposition, the substrate is typically conveyedthrough all the chambers of the coating line. It is to be appreciatedthat the coater can include a plurality of chambers aligned andconnected in this manner, regardless of the particular depositionprocesses that are performed in such chambers. Moreover, the noted ratescan be used in conveying the substrate through a coater having anytype(s) of deposition equipment (sputter equipment, CVD equipment,evaporation equipment, etc.).

The coater can optionally include different chambers adaptedrespectively for carrying out different deposition processes. Forexample, the coater can include one or more chambers in which sputteringis performed and one or more chambers in which an ion beam filmdeposition technique is performed. Further, the coater can include oneor more chambers in which sputtering is performed and one or morechambers in which chemical vapor deposition is performed. Alternatively,the coater can include one or more chambers in which chemical vapordeposition is performed and one or more chambers in which evaporation isperformed. Various alternatives of this nature will be apparent toskilled artisans given the present teaching as a guide.

In preferred embodiments, the coater includes one or more sputteringchambers. In particularly preferred embodiments, all of the chambers inthe coater are sputtering chambers. In some cases, one or more of thesputtering chambers have downward coating equipment. FIG. 6 illustratesan exemplary sputtering chamber having downward coating equipment. Theillustrated sputtering chamber 400 includes a base (or “floor”) 420, aplurality of side walls 422, and a ceiling (or “top lid” or “cover”)430, together bounding a sputtering cavity 402. Two upper targets 480 aare mounted above the path of substrate travel 45. The substrate 12 isconveyed along the path of substrate travel 45 during film deposition,optionally over a plurality of spaced-apart transport rollers.

In FIG. 6, two upper targets are provided, although this is by no meansrequired. For example, a single target or more than two targets couldalternatively be used in the chamber. Moreover, the chamber can includeplanar targets, although cylindrical targets are shown. Preferably, eachupper target 480 a is adjacent to one or more upper gas distributionpipes positioned (e.g., each having at least one gas-delivery outlet)above the path of substrate travel. Each upper target 480 a also is alsopreferably adjacent to one or more upper anodes positioned above thepath of substrate travel. Preferably, each target also includes a magnetassembly positioned adjacent the target body (mounted inside acylindrical target, mounted behind a planar target, etc.).

In other cases, as illustrated in FIG. 8, the coater includes one ormore sputtering chambers having upward coating equipment. FIG. 8illustrates an exemplary sputtering chamber having only upward coatingequipment. The illustrated sputtering chamber 600 includes a base (or“floor”) 620, a plurality of side walls 622, and a ceiling (or “top lid”or “cover”) 630, together bounding a sputtering cavity 602. Two lowertargets 680 b are mounted below the path of substrate travel 45. Thesubstrate 12 is conveyed along the path of substrate travel 45 duringfilm deposition, optionally over a plurality of spaced-apart rollers 10.The lower targets 680 b are sputtered to deposit film onto the bottomsurface of the substrate. Each upward sputtering apparatus preferably isadjacent to one or more lower gas distribution pipes positioned (e.g.,each having at least one gas-delivery outlet) below the path ofsubstrate travel 45. Optional lower anodes can be positioned below thepath of substrate travel, adjacent to at least one lower target. Eachlower target desirably comprises a magnet assembly, as described above.Particularly useful upward sputtering apparatuses are described in U.S.patent application Ser. Nos. 09/868,542, 09/868,543, 09/979,314,09/572,766, and 09/599,301, the entire contents of each of which areincorporated herein by reference.

In other cases, as illustrated in FIG. 7, the coater includes one ormore sputtering chambers having dual direction coating equipment. FIG. 7illustrates an exemplary sputtering chamber having both downward andupward coating equipment. Dual direction sputtering chambers aredescribed in U.S. patent application Ser. Nos. 09/868,542, 10/911,155,and 10/922,719, the entire teachings of each of which are incorporatedherein by reference. The illustrated sputtering chamber 500 includes abase (or “floor”) 520, a plurality of side walls 522, and a ceiling (or“top lid” or “cover”) 530, together bounding a sputtering cavity 502.Two upper targets 580 a are mounted above the path of substrate travel45 and two lower targets 580 b are mounted below the path of substratetravel. The substrate 12 is conveyed along the path of substrate travel45 during film deposition, optionally over a plurality of spaced-apartrollers 10. Here, the upper targets 580 a and the lower targets 580 bcan all be sputtered simultaneously to deposit film on both majorsurfaces of the substrate. Alternatively, the upper targets alone may beoperated, or the lower targets alone may be operated.

Exemplary coater configurations are shown in FIGS. 9-13. The coater ineach figure has a substrate support 10 defining a path of substratetravel extending through the coater. Transport rollers define theillustrated paths of substrate travel, although conveyor belts or othersubstrate supports can be used. Preferably, the path of substrate travelextends generally or substantially horizontally through the coater. Thechambers are typically connected such that the path of substrate travelextends through all the deposition chambers of the coater.

Preferably, the substrate support 10 is configured for maintaining(e.g., supporting) the substrate in a generally or substantiallyhorizontal position while the substrate is being coated (e.g., duringconveyance of the substrate through the coater). Thus, the support 10desirably is adapted to convey a sheet-like substrate, and preferablymultiple sheet-like substrates spaced-apart from one another, throughthe coater while maintaining the/each substrate in a generally orsubstantially horizontal orientation (e.g., wherein a top major surfaceof the/each substrate is oriented upwardly while a bottom major surfaceof the/each substrate is oriented downwardly).

Preferably, the substrate support 10 comprises a plurality ofspaced-apart transport rollers. Typically, at least one of the rollersis rotated (e.g., by energizing a motor operably connected to theroller) such that the substrate is conveyed along the path of substratetravel. When the substrate is conveyed on such rollers, the bottomsurface of the substrate is in direct physical (i.e., supportive)contact with the rollers. Thus, certain methods of the invention involvea glass sheet and a plurality of spaced-apart transport rollers, and themethod comprises rotating at least one of the rollers to convey theglass sheet, such that the bottom major surface of the glass sheet comesinto direct physical contact with the rollers during conveyance.

Thus, in certain embodiments, the substrate is a glass sheet that is on(e.g., positioned on top of) the support 10 during conveyance. In somecases, other glass sheets are also positioned on the support 10, and arespaced apart from one another on the support 10 and conveyed in such aspaced-apart configuration.

In embodiments where the support 10 comprises rollers, the rollers canbe of any conventional structure. It has been found that good resultscan be obtained by employing cylindrical (e.g., aluminum) tubes aboutwhich a rope is spirally wound, such rope providing the surface withwhich the substrate is in direct contact. The rope, for example, can beformed of Kevlar™, i.e., poly-para-phenylene terephthalamide, or anotherpolymer (e.g., nylon-like polymer). Preferably, a high melting pointpolymer is used (e.g., a polymer having a melting point above themaximum processing temperature established in the desired depositionprocess, e.g., at least about 165 degrees C., more preferably at leastabout 200 degrees C., and perhaps optimally at least about 400 degreesC.). Cylinders carrying a spirally-wound rope (or a plurality ofindividual bands) are particularly desirable for embodiments wherein anupward coating process is performed, as the rope reduces the area ofcontact between the rollers and the substrate's bottom surface and thusprovides a particularly non-damaging support for the substrate'sfreshly-coated bottom surface. Thus, in certain embodiments, thesubstrate support comprises a plurality of spaced-apart rollers eachcomprising at least one rope disposed about a cylinder.

In embodiments where the support 10 comprises spaced-apart rollers, thespacing of the rollers is preferably kept fairly small to permit smallsubstrates to be processed without any significant risk of having thesubstrates fall between the rollers. The maximum safe spacing ispreferably determined on a case-by-case basis for a desired range ofsubstrate sizes.

While small substrates can be coated, the invention is advantageous forprocessing large-area substrates, such as glass sheets for architecturaland automotive glass applications. Thus, in certain methods of theinvention, the substrate conveyed through the coater is a large-areasubstrate having a major dimension (e.g., a length or width) of at leastabout 0.5 meter, at least 1 meter, at least 1.5 meters, or at least 2meters. With large-area substrates in particular (especially thoseformed of glass), it is advantageous to convey the substrate through thecoater in a generally or substantially horizontal orientation.

In some embodiments, the coater only includes chambers (or bays) havingdownward coating equipment. In other embodiments, the coater alsoincludes chambers having upward coating equipment. The coater in FIG. 9only has downward coating equipment. The downward coating equipment isadapted for coating a top major surface 18 of a substrate 12. Thus, thedownward coating equipment preferably is above the path of substratetravel 45. In certain embodiments, the coater is a vacuum coater and thedownward coating equipment comprises at least one downwardvacuum-coating apparatus. Each downward coating apparatus in FIG. 9 canbe any type of downward coating apparatus. Preferably, the coaterincludes at least one downward sputtering apparatus comprising an uppersputtering target located above the path of substrate travel. In someembodiments, each downward sputtering apparatus comprises two uppertargets above the path of travel, as described with reference to theembodiments of FIG. 6. In certain embodiments, all the downwarddeposition devices D1-D36 in FIG. 9 are sputtering devices.

In certain embodiments, the coater of FIG. 9 includes at least onedeposition chamber having a downward chemical vapor deposition (CVD)apparatus. Such an apparatus may comprise a gas delivery system fordelivering precursor gas to the upper region of the coater (i.e., theregion of the coater above the path of substrate travel). Preferably,such an apparatus comprises a gas-delivery outlet located above the pathof substrate travel, such that from the precursor gas, coating materialcondenses upon the top surface 18 of the substrate 10. A CVD apparatusof this nature will typically comprise a gas supply from which theprecursor gas is delivered through a gas line, out of the gas outlet,and into the upper region of the coater. If so desired, such a downwardchemical vapor deposition apparatus can be a plasma-enhanced chemicalvapor deposition apparatus of the type described in U.S. patentapplication Ser. No. 10/373,703, entitled “Plasma-Enhanced FilmDeposition” (Hartig), the entire teachings of which are incorporatedherein by reference.

In certain embodiments, the coater of FIG. 9 includes at least onedeposition chamber having a downward coating apparatus comprising an iongun. An upper ion gun of this nature can be adapted for carrying out anydesired ion-assisted deposition (IAD) process. For example, such an iongun can be adapted for direct film deposition. Alternatively, such anion gun can be part of an ion beam sputter deposition source comprisingan upper sputtering target against which the ion gun accelerates ions,such that atoms of the target material are ejected from the targetdownwardly toward the substrate's top surface. These types of IADmethods are known in the art, as are many other suitable IAD methods.

The deposition chambers of a coater can be grouped into coat zones. Eachcoat zone can include any number of chambers or bays. The specificconfiguration of the coater (e.g., its number of deposition chambers)will vary depending on the particular type of coater used and theparticular type of coating desired. Generally, the coater includes atleast 20 deposition chambers, optionally arranged along a linear path ofsubstrate travel. In preferred embodiments, the coater includes at least36 deposition chambers, at least 39 deposition chambers, at least 42deposition chambers, at least 45 deposition chambers, at least 55deposition chambers, at least 60 deposition chambers, or at least 63deposition chambers. The exemplary coaters of FIGS. 9-12 have at least36 deposition chambers, and the exemplary coater of FIG. 13 has at least63 deposition chambers.

FIG. 10 illustrates a coater with some chambers having downward coatingequipment and other chambers having upward coating equipment. Here, thecoater preferably can be operated (i.e., it preferably is adapted) tocoat the entirety of both major surfaces of a sheet-like substrate in asingle pass of the substrate through the coater. The downward coatingequipment can, for example, be the types of downward coating equipmentdescribed above with reference to FIG. 9. With respect to the upwardcoating equipment, each upward coating apparatus preferably is mountedbelow the path of substrate travel and is adapted for coating the bottomsurface of the substrate.

Each upward coating apparatus in FIG. 10 can be any type of upwardcoating apparatus. In certain embodiments, the coater includes at leastone upward sputtering apparatus. In these embodiments, each upwardsputtering apparatus includes a lower sputtering target below the pathof substrate travel. Useful upward sputtering apparatuses are describedin U.S. patent application Ser. Nos. 09/868,542, 09/868,543, 09/979,314,09/572,766, and 09/599,301, the entire contents of each of which areincorporated herein by reference. In some cases, the upward sputteringapparatus comprises two lower targets mounted beneath the path ofsubstrate travel, as described with reference to FIG. 8. In preferredembodiments, all the upward U1-U6 and downward D1-D30 deposition devicesare sputtering devices.

In certain embodiments, the coater of FIG. 10 includes at least oneupward evaporation coating apparatus. Such an apparatus may comprise asource of coating material to be evaporated, the source typically beinglocated beneath the path of substrate travel. This source of materialcan be provided in the form of a boat, crucible, strip, or coil thatcontains, or is formed of, the desired source material. Such anapparatus typically also comprises means for delivering energy to thesource material. For example, the source material can be provided inconjunction with a heat source (e.g., a heating element) adapted forheating the source material by direct or indirect resistance, thermalconduction, radiation or induction, electron beam, laser irradiation, orarcing. Various processes and apparatuses are known in the art forcoating substrates by upward evaporation.

In other embodiments, the coater of FIG. 10 includes at least one upwardCVD apparatus. Such an apparatus may comprise a gas delivery system fordelivering precursor gas to the lower region of the coater. Preferably,such an apparatus comprises a gas-delivery outlet located below the pathof the substrate travel, such that from the precursor gas, coatingmaterial condenses upon the bottom surface of the substrate 12. A CVDapparatus of this nature will typically comprise a gas supply from whichthe precursor gas is delivered through the gas line, out of the gasoutlet, and into the lower region of the coater.

In certain preferred embodiments, the coater of FIG. 10 includes atleast one upward coating apparatus comprising an ion gun. A lower iongun of this nature can be adapted for carrying out any desired IADprocess. For example, such an ion gun can be adapted for carrying outdirect film deposition. Alternatively, such an ion gun can be part of anion beam sputter deposition source comprising a lower sputtering targetagainst which the ion gun accelerates ions, such that atoms of thetarget material are ejected from the target upwardly toward thesubstrate's bottom surface. These types of IAD methods are known in theart, as are many other suitable IAD methods. In one embodiment, thecoater includes one or more lower ion guns adapted for carrying out anion-assisted evaporation technique. Reference is made to the publication“Ion-Based Methods For Optical Thin Film Deposition” (Journal ofMaterial Science; J. P. Marting, 21 (1986) 1-25), the entire contents ofwhich are incorporated herein by reference.

Preferably, each upward coating apparatus is positioned beneath (e.g.,directly underneath) a gap between an adjacent pair of transport rollers10. The gap may result from conventional transport roller spacing.Alternatively, this gap may be wider than conventional roller spacing.This can be accomplished by mounting the rollers that define each suchgap further apart and/or by decreasing the size of these rollers.

In some embodiments, the downward and upward coating equipment in acoater (e.g., like that of FIG. 10, FIG. 11, or FIG. 13) can both be thesame basic type of coating equipment (e.g., all the film depositionequipment in the coater can be sputtering equipment). Alternatively, thedownward coating equipment can be one type of coating equipment, whilethe upward coating equipment is another type of coating equipment (e.g.,the downward coating equipment can be conventional magnetron sputteringequipment, while the upward coating equipment is ion beam filmdeposition equipment). As another alternative, the upward coatingequipment and/or the downward coating equipment can include acombination of different types of coating equipment (e.g., the coatercan have some upward sputtering equipment and some upward evaporationequipment).

FIG. 11 illustrates a coater with some chambers that only have downwardcoating equipment and other chambers that have both downward and upwardcoating equipment. The downward coating equipment can be any typesdescribed with reference to FIG. 9, and the upward coating equipment canbe any types described with reference to FIG. 10. In some cases, thedownward and upward coating equipment in the dual-direction depositionchambers are the same or similar types of coating equipment (e.g., theymay all be sputtering devices), although this is not required.

The coaters exemplified in FIGS. 9-11 preferably are used to deposit alow-emissivity coating having three infrared-reflection or more layers.Downward coating equipment preferably is used to deposit thelow-emissivity coating. When downward coating equipment is operated todeposit a low-emissivity coating on a substrate's top surface 18, themethod typically involves applying films of reflective metal betweentransparent dielectric films. In some cases, this involves depositing atleast seven film regions having the following sequence of films (e.g.,moving outwardly from surface 18): a first transparent dielectric filmregion 20, a first infrared-reflection film region 100, a thirdtransparent dielectric film region 40, a second infrared-reflection filmregion 200, a third transparent dielectric film region 60, a thirdinfrared-reflection film region 300, and a fourth transparent dielectricfilm region 80. The method can optionally include depositing blockerlayers 105, 205 and 305 over the infrared-reflection film regions.

In certain embodiments, downward coating equipment is operated todeposit a low-emissivity coating, and the method involves depositing atleast 50 angstroms, or at least 100 angstroms, of transparent dielectricfilm between the surface 18 of the substrate and a firstinfrared-reflection film region 100, depositing at least 100 angstromsof transparent dielectric film between the first 100 and a second 200infrared-reflection film regions, depositing at least 100 angstroms oftransparent dielectric film between the second 200 and a third 300infrared-reflection film regions, and depositing at least 50 angstroms,or at least 100 angstroms, of transparent dielectric film over the thirdinfrared-reflection film region 300. In some cases, the downward coatingequipment is operated to deposit less than 175 angstroms of transparentdielectric film between the top surface 18 of the substrate and thefirst infrared-reflection film region 100. In one embodiment, thedownward coating equipment is operated to deposit at least 400 angstromsof transparent dielectric film between the first 100 and second 200infrared-reflection film regions, and to deposit at least 400 angstromsof transparent dielectric film between the second 200 and third 300infrared-reflection film regions.

With reference to FIGS. 10, 11, and 13, upward coating equipment can beused to deposit a desired coating on a bottom surface of a substrate 12.Preferably, both a low-emissivity coating and the desired coating aredeposited during a single pass of the substrate through the coater. Thedesired coating can include, for example, a sequence of film regionscharacterized by, moving away from the bottom surface of the substrate,a primary film region comprising a first transparent dielectric materialand a secondary film region comprising a second transparent dielectricmaterial.

In some embodiments, the coater can be operated to deposit alow-emissivity coating on the top surface of the substrate, and todeposit a surface-effect coating on the bottom surface of the substrate.When provided, the surface-effect coating preferably is selected fromthe group consisting of a photocatalytic coating, a hydrophilic coating,and a hydrophobic coating. In certain embodiments, there is provided asurface-effect coating comprising titanium oxide and/or silicon oxide.In one embodiment, the surface-effect coating is a photocatalyticcoating comprising titanium oxide (e.g., TiO₂)

Photocatalytic coatings typically comprise a semiconductor that canabsorb ultraviolet radiation and can photocatalytically degrade organicmaterials such as oil, plant matter, fats, and greases. The mostpowerful of the photocatalysts appears to be titanium oxide (e.g.,titanium dioxide). Useful photocatalytic coatings are described in U.S.Pat. No. 5,874,701 (Watanabe et al), U.S. Pat. No. 5,853,866 (Watanabeet al), U.S. Pat. No. 5,961,843 (Hayakawa et al.), U.S. Pat. No.6,139,803 (Watanabe et al), U.S. Pat. No. 6,191,062 (Hayakawa et al.),U.S. Pat. No. 5,939,194 (Hashimoto et al.), U.S. Pat. No. 6,013,372(Hayakawa et al.), U.S. Pat. No. 6,090,489 (Hayakawa et al.), U.S. Pat.No. 6,210,779 (Watanabe et al), U.S. Pat. No. 6,165,256 (Hayakawa etal.), and U.S. Pat. No. 5,616,532 (Heller et al.), as well as U.S.patent application Ser. Nos. 11/179,178 and 11/179,852, the contents ofeach of which are incorporated herein by reference for their teachingsof exemplary photocatalytic coatings and useful deposition methods.

Thus, in certain embodiments, the coater includes upward coatingequipment adapted for applying a photocatalytic coating, optionally onecomprising titania. The upward coating equipment can, for example,comprise a source or sources of titanium and oxygen. For example, theupward coating equipment can optionally include a lower sputteringtarget comprising titanium (e.g., metallic titanium or titanium oxide).Conjointly, the lower region of the coater adjacent such a target canoptionally be provided with an oxidizing atmosphere. In one embodiment,the upward coating equipment comprises at least one lower sputteringtarget of the nature described in U.S. patent application 60/262,878,the entire teachings of which are incorporated herein by reference.

When a low-emissivity coating and a surface-effect coating are depositedin a coater like that of FIG. 11, a portion (e.g., less than theentirety) of the low-emissivity coating and the entirety of thesurface-effect coating are deposited simultaneously. For example,downward deposition equipment D31-D36 can be operated at the same timeas upward deposition equipment U1-U6. On the other hand, when alow-emissivity coating and a surface-effect coating are deposited in acoater like that of FIG. 10, they are deposited sequentially (e.g., thelow-emissivity coating can be deposited first by downward sputtering,then the surface-effect coating can be deposited by upward sputtering,all during a single pass of the substrate through the coater) or evenintermixed. Intermixing means that the upward deposition and downwarddeposition can be performed at the same location (e.g., in the samesputtering bay) provided that by layer stack design the materials areused in the same order of application.

Turning now to FIG. 12, there is described an exemplary method fordepositing a high infrared-reflection coating 7 in accordance withcertain embodiments of the invention. The coater shown schematically inFIG. 12 is used to deposit a coating 7 that includes, in sequence frommajor surface 18 outwardly, a first transparent dielectric film region20 comprising zinc tin oxide, a first infrared-reflection film region100 comprising silver, a first blocker film region 105 comprisingtitanium, a second transparent dielectric film region 40 comprising zinctin oxide, a second infrared-reflection film region 200 comprisingsilver, a second blocker film region 205 comprising titanium, a thirdtransparent dielectric film region 60 comprising zinc tin oxide, a thirdinfrared-reflection film region 300 comprising silver, a third blockerfilm region 305 comprising titanium, and a fourth transparent dielectricfilm region 80 that includes an outermost layer comprising siliconnitride over a layer comprising zinc tin oxide.

With continued reference to FIG. 12, the substrate 12 is positioned atthe beginning of the coater and conveyed into the first coat zone CZ1(e.g., by conveying the substrate along transport rollers forming thesubstrate support 10). This coat zone CZ1 has three sputtering chambers(or “bays”), C1 through C3, which are adapted collectively to deposit afirst transparent dielectric film region 20 comprising zinc tin oxide.All three of these bays are provided with sputtering targets comprisinga compound of zinc and tin. Each of these bays is illustrated as havingtwo cylindrical sputtering targets, although the number and type (e.g.,cylindrical versus planar) can be varied as desired. These first sixtargets are sputtered in an oxidizing atmosphere to deposit the firsttransparent dielectric film region 20 in the form of an oxide filmcomprising zinc and tin. The oxidizing atmosphere can consistessentially of oxygen (e.g., about 100% O₂) at a pressure of about4×10⁻³ mbar. Alternatively, this atmosphere may comprise argon andoxygen. With reference to Table 5 below, a power of about 36.7 kW isapplied to the first two targets, a power of about 34.6 kW is applied tothe second two targets, and a power of about 35.5 kW is applied to thethird two targets. The substrate 12 is conveyed beneath all six of thesetargets at a rate of about 310 inches per minute, while sputtering eachtarget at the described power level, thereby depositing the firsttransparent dielectric film region 20 in the form of an oxide filmcomprising zinc and tin and having a thickness of about 159 angstroms.

The substrate 12 is then conveyed into a second coat zone CZ2 whereinthe first infrared-reflection film region 100 is applied directly overthe first transparent dielectric film region 20. The second coat zoneCZ2 is provided with an inert atmosphere (e.g., argon at a pressure ofabout 4×10⁻³ mbar). The active sputtering bays C4 and C5 in this coatzone CZ2 each have a planar target, although the number and type oftargets here can be changed. The target in bay C4 is a metallic silvertarget, and the target in bay C5 is a metallic titanium target. Thesubstrate is conveyed beneath the silver target at a rate of about 310inches per minute, while sputtering this target at a power of about 7.1kW, thereby depositing the first infrared-reflection film region 20 inthe form of a silver film having a thickness of about 122 angstroms. Thesubstrate is then conveyed beneath the titanium target in bay C5, whilesputtering this target at a power of about 7.8 kW, thereby depositing afirst blocker film region 105 in the form of a film comprising titaniumand having a thickness of about 20 angstroms.

The substrate 12 is then conveyed through a third coat zone CZ3, afourth coat zone CZ4, and a fifth coat zone CZ5, in which zones thesecond transparent dielectric film region 40 is applied in the form ofan oxide film comprising zinc and tin. The third CZ3 and fourth CZ4 coatzones each have three active sputtering bays. The fifth coat zone CZ5has two active sputtering bays (there may, for example, be unused baysalong the way). In each of the bays C6-C13, there are mounted twocylindrical targets each comprising (i.e., including a sputterabletarget material comprising) a compound of zinc and tin. Each of thesesputtering bays C6-C13 is provided with an oxidizing atmosphere. Forexample, the oxidizing atmospheres in the third CZ3, fourth CZ4, andfifth CZ5 coat zones can each consist essentially of oxygen (e.g., about100% 02) at a pressure of about 4×10⁻³ mbar. Alternatively, one or moreof these atmospheres can comprise argon and oxygen.

As shown in Table 5 below, a power of about 50.2 kW is applied to thefirst two targets in the third coat zone CZ3, a power of about 45.1 kWis applied to the second two targets in this coat zone CZ3, and a powerof about 49.5 kW is applied to the third two targets in this zone CZ3.Here, a power of about 53.1 kW is applied to the first two targets inthe fourth coat zone CZ4, a power of about 47.7 kW is applied to thesecond two targets in this coat zone CZ4, and a power of about 44.8 isapplied to the third two targets in this zone CZ4. Further, a power ofabout 49.0 kW is applied to the first two targets in the fifth coat zoneCZ5, and a power of about 45.6 kW is applied to the second two targetsin this coat zone CZ5. The substrate 12 is conveyed beneath all of thenoted targets in coat zones 3-5 (i.e., CZ3 through CZ5), while conveyingthe substrate at a rate of about 310 inches per minute and sputteringeach target at the noted power level, such that the second transparentdielectric film region 40 is applied in the form of an oxide filmcomprising zinc and tin and having a thickness of about 562 angstroms.

The substrate 12 is then conveyed into a sixth coat zone CZ6 where thesecond infrared-reflection film region 200 is applied directly over thesecond transparent dielectric film region 40. The sixth coat zone CZ6has an inert atmosphere (e.g., argon at a pressure of about 4×10⁻³mbar). The sputtering bays C14, C15 in this coat zone CZ6 each have aplanar target. The target in bay C14 is a metallic silver target, andthe target in chamber C15 is a metallic titanium target. A power ofabout 8.9 kW is applied to the silver target, while the substrate isconveyed beneath this target at a rate of about 310 inches per minute,to deposit the second infrared-reflection film region 200 as a metallicsilver film having a thickness of about 149 angstroms. The substrate isthen conveyed beneath the metallic titanium target in bay C15, with apower of about 8.1 kW being applied to this target to deposit a secondblocker film region 205 comprising titanium and having a thickness ofabout 20 angstroms.

The substrate 12 is then conveyed through a seventh coat zone CZ7, aneighth coat zone CZ8, and a ninth coat zone CZ9, wherein collectivelythe third transparent dielectric film region 60 is applied. Each ofthese coat zones has three sputtering bays, and each such bay isprovided with two cylindrical targets (bays C16 through C18 are in CZ7,bays C19 through C21 are in CZ8, and bays C22 through C24 are in CZ9).The targets here all comprise a sputterable material that is a compoundof zinc and tin. Each of these coat zones is provided with an oxidizingatmosphere consisting essentially of oxygen (e.g., about 100% O₂ at apressure of about 4×10⁻³ mbar). Alternatively, this atmosphere maycomprise argon and oxygen.

A power of about 50.3 kW is applied to the first two targets in theseventh coat zone CZ7, a power of about 45.5 kW is applied to the secondtwo targets in this coat zone, and a power of about 48.9 kW is appliedto the third two targets in this zone. A power of about 52.5 kW isapplied to the first two targets in the eighth coat zone CZ8, while apower of about 48.2 kW is applied to the second two targets in this coatzone, and a power of about 44.7 kW is applied to the third two targetsin this zone. A power of about 49.0 kW is applied to the first twotargets in the ninth coat zone CZ9, while a power of about 45.5 kW isapplied to the second two targets in this coat zone, and a power ofabout 47.8 kW is applied to the third two targets in this zone. Thesubstrate is conveyed beneath all of these targets (i.e., beneath allthe targets in CZ7-CZ8) at about 310 inches per minute, while sputteringeach target at the noted power level, such that the third transparentdielectric film region 60 is applied as an oxide film comprising zincand tin and having a thickness of about 655 angstroms.

The substrate is then conveyed into a tenth coat zone CZ10 where thethird infrared-reflection film region 300 is applied. This coat zonecontains an inert atmosphere (e.g., argon at a pressure of about 4×10⁻³mbar). The active bays C25, C26 in this coat zone are each provided witha planar target. The target in bay C25 is a metallic silver target, andthe target in bay C26 is a metallic titanium target. A power of about12.6 kW is applied to the silver target, while the substrate is conveyedbeneath this target at a rate of about 310 inches per minute, therebydepositing the third infrared-reflection film region 300 as a silverfilm having a thickness of about 206 angstroms. The substrate is thenconveyed beneath the titanium target in chamber C26, while sputteringthat target at a power level of about 8.1 kW so as to deposit a thirdblocker film region 305 in the form of a film comprising titanium andhaving a thickness of about 20 angstroms.

The substrate 12 is then conveyed through an eleventh coat zone CZ11, atwelfth coat zone CZ12, and a thirteenth coat zone CZ13, whereincollectively there is deposited the fourth transparent dielectric filmregion 80. The eleventh coat zone C11 has three sputtering bays, eachwith two cylindrical targets (bays C27 through C29 are in CZ11). Thetwelfth coat zone C12 has only one active sputtering bay C30, and thisbay C30 is provided with two cylindrical targets (bay C30 is in CZ12).The thirteenth coat zone CZ13 has three sputtering bays, each providedtwo cylindrical targets (bays C31 through C33 are in CZ13). Each of thenoted targets in coat zones CZ11 through CZ13 comprises a sputterabletarget material that is a compound of zinc and tin. The coat zones CZ11through CZ13 are all provided with oxidizing atmospheres, eachconsisting essentially of oxygen (e.g., about 100% O₂ at a pressure ofabout 4×10⁻³ mbar). Alternatively, one or more of these atmospheres cancomprise argon and oxygen.

A power of about 17.9 kW is applied to the first two targets in theeleventh coat zone CZ11, a power of about 21.1 kW is applied to thesecond two targets in this coat zone CZ11, and a power of about 19.6 kWis applied to the third two targets in this zone CZ11. A power of about20.1 kW is applied to the two targets in the twelfth coat zone CZ12. Apower of about 21.5 kW is applied to the first two targets in thethirteenth coat zone CZ13, a power of about 19.4 kW is applied to thesecond two targets in this coat zone CZ13, and a power of about 19.3 kWis applied to the third two targets in this zone CZ13. The substrate isconveyed beneath all the targets in CZ11-CZ13 at a rate of about 310inches per minute, while sputtering each of these targets at the notedpower level, such that an inner portion of the fourth transparentdielectric film region 80 is applied as an oxide film comprising zincand tin and having at a thickness of about 236 angstroms.

Finally, the substrate is conveyed into a fourteenth coat zone CZ14,wherein the outermost portion of the fourth transparent dielectric filmregion 80 is applied. This coat zone CZ14 has three sputtering baysC34-C36, each containing a nitrogen atmosphere, optionally with someargon, at a pressure of about 4×10⁻³ mbar. The sputtering bays C34-C36in this coat zone CZ14 are each provided with two cylindrical targets.Each of these targets comprises a sputterable target material of siliconwith a small amount of aluminum. A power of about 31.9 kW is applied tothe first two targets in the fourteenth coat zone CZ14, a power of about34.0 kW is applied to the second two targets in this coat zone CZ14, anda power of about 37.4 kW is applied to the third two targets in thiszone CZ14. The substrate is conveyed beneath all the targets in CZ14 atabout 310 inches per minute, while sputtering each of these targets atthe noted power level, such that the outermost portion of the fourthtransparent dielectric film region 80 is applied as a nitride filmcomprising silicon and a small amount of aluminum and having a thicknessof about 101 angstroms.

TABLE 5 Chamber Power (kW) C1 36.7 C2 34.6 C3 35.5 C4 7.1 C5 7.8 C6 50.2C7 45.1 C8 49.5 C9 53.1 C10 47.7 C11 44.8 C12 49 C13 45.6 C14 8.9 C158.1 C16 50.3 C17 45.5 C18 48.9 C19 52.5 C20 48.2 C21 44.7 C22 49.0 C2345.5 C24 47.8 C25 12.6 C26 8.1 C27 17.9 C28 21.1 C29 19.6 C30 20.1 C3121.5 C32 19.4 C33 19.3 C34 31.9 C35 34.0 C36 37.4

Table 6 below illustrates another exemplary film stack that can be usedas the present coating 7:

TABLE 6 FILM STACK E Glass Zn + O 159 Å Ag 122 Å Ti  20 Å Zn + O 562 ÅAg 149 Å Ti  20 Å Zn + O 235 Å Si3N4 185 Å Zn + O 235 Å Ag 206 Å Ti  20Å Zn + O 236 Å Si3N4 101 Å

The film stack of Table 6 exemplifies a group of embodiments wherein thelow-emissivity coating is deposited so as to include two film regionscomprising transparent dielectric nitride film (optionally consistingessentially of nitride film). These nitride films can, for example,comprise silicon nitride.

In the present embodiments, an infrared-reflective film region canoptionally be deposited between the two nitride films. These nitridefilms (and the infrared-reflective film region between them) arepreferably part of a coating comprising, moving outwardly from the topmajor surface of the substrate, a first transparent dielectric filmregion, a first infrared-reflective film region comprising silver, asecond transparent dielectric film region, a second infrared-reflectivefilm region comprising silver, a third transparent dielectric filmregion, a third infrared-reflective film region comprising silver, and afourth transparent dielectric film region. In Table 6, the third silverfilm is located between the two nitride films. Alternatively, the secondsilver film may be located between two nitride films, or the second andthird silver films may both be located between two nitride films.

In some related method embodiments, the method involves sputtering twoseries of upper targets in nitriding gas to reactively sputter depositthe two noted nitride films over a top major surface of a substrate. Incertain cases, the reactive sputter deposition of the two nitride filmsresults in a combined thickness of at least 100 angstroms, at least 150angstroms, or at least 200 angstroms, for these two films.

The present embodiments can optionally involve simultaneously sputteringsilver in at least three chambers adapted for downward sputtering.Typically, these three chambers will be separated from one another byother chambers that contain reactive sputtering atmospheres and areadapted for sputter depositing transparent dielectric film. This mayinvolve applying an average power of greater than 8.5 kW, or greaterthan 9.0 kW, on three upper sputtering targets comprising sputterablesilver. The deposition methods associated with the present embodimentsmay involve a coater having an extended series of sputtering chambers,which in certain embodiments includes at least 63 sputtering chambers.

In some of the coating embodiments disclosed herein, the coating may bedeposited by sputter depositing dielectric film directly over at leastone infrared-reflective film region comprising (optionally consistingessentially of) silver. Here, instead of depositing metallic blockerfilm directly over each infrared-reflective film region, dielectric filmis deposited directly over at least one (or in some cases, over each) ofthe infrared-reflective film regions. These embodiments may beparticularly desirable, for example, when exceptionally high visibletransmission is desired. While the thickness of this type of dielectricfilm can be varied as desired, some embodiments involve a thickness of75 angstroms or less, or 50 angstroms or less. Other useful thicknessesand details (associated with depositing dielectric film directly over aninfrared-reflective film) are described above.

While there have been described what are believed to be preferredembodiments of the present invention, those skilled in the art willrecognize that other and further changes and modifications can be madewithout departing from the spirit of the invention, and all such changesand modifications should be understood to fall within the scope of theinvention.

What is claimed is:
 1. A method for depositing film onto a glass sheet,the method comprising: a) providing a coater having a path of substratetravel extending through the coater, the coater including downwardcoating equipment mounted above the path of substrate travel; b)conveying the glass sheet along the path of substrate travel in agenerally horizontal orientation wherein a top major surface of theglass sheet is oriented upwardly and a bottom major surface of the glasssheet is oriented downwardly; and c) operating the downward coatingequipment to deposit upon the top major surface of the glass sheet acoating including a sequence of at least seven film regions comprising,moving outwardly from the top major surface of the glass sheet, a firsttransparent dielectric film region, a first infrared-reflective filmregion comprising silver, a second transparent dielectric film region, asecond infrared-reflective film region comprising silver, a thirdtransparent dielectric film region, a third infrared-reflective filmregion comprising silver, and a fourth transparent dielectric filmregion; the method comprising depositing said at least seven filmregions in a single pass of the glass sheet through the coater, andwherein during this single pass the glass sheet is conveyed at aconveyance rate of 400 inches per minute or faster.
 2. The method ofclaim 1 wherein the first, second, and third infrared-reflective filmregions comprising silver are each deposited at a thickness of betweenabout 50 angstroms and about 300 angstroms.
 3. The method of claim 1wherein each of the first, second, and third transparent dielectric filmregions comprises an oxide layer in contact with one of theinfrared-reflective film regions comprising silver, and each such oxidelayer comprises zinc tin oxide having a metal-only ratio of tin weightdivided by total zinc plus tin weight of greater than 0 but less than0.3.
 4. The method of claim 1 wherein said operating the downwardcoating equipment includes sputter depositing dielectric film directlyover each infrared-reflective film region comprising silver.
 5. Themethod of claim 4 wherein said dielectric film directly over eachinfrared-reflective film region is deposited at a thickness of 75angstroms or less.
 6. The method of claim 1 wherein said operating thedownward coating equipment includes simultaneously sputtering silver inat least three chambers adapted for downward sputtering.
 7. The methodof claim 1 wherein said conveyance rate is maintained substantiallyconstant throughout an entirety of said single pass of the glass sheetthrough the coater
 8. The method of claim 1 wherein the coater comprisessputtering chambers that have the downward coating equipment.
 9. Themethod of claim 1 wherein the coater comprises more than 36 sputteringchambers.
 10. The method of claim 1 wherein the coater has an extendedseries of sputtering chambers and includes upward coating equipmentmounted below the path of substrate travel, the upward coating equipmentcomprising lower sputter targets mounted at a lower elevation than thepath of substrate travel, the downward coating equipment comprisingupper sputter targets mounted at a higher elevation than the path ofsubstrate travel, wherein the coater's extended series of sputteringchambers includes at least 39 downward sputtering chambers eachincluding at least one of the upper sputter targets.
 11. The method ofclaim 10 wherein the coater's extended series of sputtering chambersincludes at least 55 sputtering chambers.
 12. The method of claim 1wherein the coater has an extended series of sputtering chambersincluding at least 60 sputtering chambers, the glass sheet has a majordimension of at least 2 meters, and the method comprises entirelycoating both the top and bottom major surfaces of the glass sheet insaid single pass of the glass sheet through the coater.
 13. The methodof claim 1 wherein said single pass of the glass sheet through thecoater is continuous in that the glass sheet is not interrupted byremoving the glass sheet from the coater during said single pass. 14.The method of claim 1 wherein said coating including the sequence of atleast seven film regions comprises a plurality of nitride films, andwherein a coating consisting essentially of oxide film(s) is depositedon the bottom major surface of the glass sheet.